diff --git a/config/feature_flags/development/invert_omniauth_args_merging.yml b/config/feature_flags/development/invert_omniauth_args_merging.yml
deleted file mode 100644
index 1a5d0a085411f6853a1ef2046ff619a8438f64be..0000000000000000000000000000000000000000
--- a/config/feature_flags/development/invert_omniauth_args_merging.yml
+++ /dev/null
@@ -1,8 +0,0 @@
----
-name: invert_omniauth_args_merging
-introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/135770
-rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/430348
-milestone: '16.6'
-type: development
-group: group::authentication
-default_enabled: false
diff --git a/ee/app/models/saml_provider.rb b/ee/app/models/saml_provider.rb
index 8dedee8047802fdbd47d9c7089550e12ccea70bd..d7a24ea96606c3dfed0cee2311e44541a69acf0e 100644
--- a/ee/app/models/saml_provider.rb
+++ b/ee/app/models/saml_provider.rb
@@ -27,7 +27,7 @@ def settings
     defaults.to_h.merge(
       idp_cert_fingerprint: certificate_fingerprint,
       idp_sso_target_url: sso_url,
-      attribute_statements: ::Gitlab::Auth::Saml::Config.default_attribute_statements
+      attribute_statements: { nickname: %w[username nickname] }
     )
   end
 
diff --git a/ee/spec/models/saml_provider_spec.rb b/ee/spec/models/saml_provider_spec.rb
index 44cd7b8944e056f2c583fcc88c9f4c0a6cb94ed8..8964459f2dcf763aba55d51bb42a5ca761018c04 100644
--- a/ee/spec/models/saml_provider_spec.rb
+++ b/ee/spec/models/saml_provider_spec.rb
@@ -2,7 +2,7 @@
 
 require 'spec_helper'
 
-RSpec.describe SamlProvider, feature_category: :system_access do
+RSpec.describe SamlProvider do
   let(:group) { create(:group) }
 
   subject(:saml_provider) { create(:saml_provider, group: group) }
@@ -155,8 +155,8 @@
       expect(settings[:idp_sso_target_url]).to eq saml_provider.sso_url
     end
 
-    it 'includes default attribute statements' do
-      expect(settings[:attribute_statements]).to match_array(::Gitlab::Auth::Saml::Config.default_attribute_statements)
+    it 'includes nickname attribute statements' do
+      expect(settings[:attribute_statements][:nickname]).to match_array(%w[nickname username])
     end
 
     context 'when saml_message_max_byte_size present in gitlab settings ' do
diff --git a/lib/gitlab/auth/saml/config.rb b/lib/gitlab/auth/saml/config.rb
index e6c9f04eff5d6607ec0e41f97144d8df7c247851..7524d8b9f85871b22daf46f505362868a946e35c 100644
--- a/lib/gitlab/auth/saml/config.rb
+++ b/lib/gitlab/auth/saml/config.rb
@@ -8,21 +8,6 @@ class << self
           def enabled?
             ::AuthHelper.saml_providers.any?
           end
-
-          def default_attribute_statements
-            defaults = OmniAuth::Strategies::SAML.default_options[:attribute_statements].to_hash.deep_symbolize_keys
-            defaults[:nickname] = %w[username nickname]
-            defaults[:name] << 'http://schemas.xmlsoap.org/ws/2005/05/identity/claims/name'
-            defaults[:name] << 'http://schemas.microsoft.com/ws/2008/06/identity/claims/name'
-            defaults[:email] << 'http://schemas.xmlsoap.org/ws/2005/05/identity/claims/emailaddress'
-            defaults[:email] << 'http://schemas.microsoft.com/ws/2008/06/identity/claims/emailaddress'
-            defaults[:first_name] << 'http://schemas.xmlsoap.org/ws/2005/05/identity/claims/givenname'
-            defaults[:first_name] << 'http://schemas.microsoft.com/ws/2008/06/identity/claims/givenname'
-            defaults[:last_name] << 'http://schemas.xmlsoap.org/ws/2005/05/identity/claims/surname'
-            defaults[:last_name] << 'http://schemas.microsoft.com/ws/2008/06/identity/claims/surname'
-
-            defaults
-          end
         end
 
         DEFAULT_PROVIDER_NAME = 'saml'
diff --git a/lib/gitlab/omniauth_initializer.rb b/lib/gitlab/omniauth_initializer.rb
index 0bcd5b1196a3566a5bddf115c0267a65ee0c555f..81ad7a7f9e1eab2d110648ceafef2f94eec76da3 100644
--- a/lib/gitlab/omniauth_initializer.rb
+++ b/lib/gitlab/omniauth_initializer.rb
@@ -29,8 +29,6 @@ def default_arguments_for(provider_name)
           {
             authorize_params: { gl_auth_type: 'login' }
           }
-        when ->(provider_name) { AuthHelper.saml_providers.include?(provider_name.to_sym) }
-          { attribute_statements: ::Gitlab::Auth::Saml::Config.default_attribute_statements }
         else
           {}
         end
@@ -63,7 +61,7 @@ def arguments_for(provider)
         provider_arguments.concat arguments
         provider_arguments << defaults unless defaults.empty?
       when Hash, GitlabSettings::Options
-        hash_arguments = merge_hash_defaults_and_args(defaults, arguments)
+        hash_arguments = arguments.deep_symbolize_keys.deep_merge(defaults)
         normalized = normalize_hash_arguments(hash_arguments)
 
         # A Hash from the configuration will be passed as is.
@@ -82,13 +80,6 @@ def arguments_for(provider)
       provider_arguments
     end
 
-    def merge_hash_defaults_and_args(defaults, arguments)
-      return arguments.to_hash if defaults.empty?
-      return defaults.deep_merge(arguments.deep_symbolize_keys) if Feature.enabled?(:invert_omniauth_args_merging)
-
-      arguments.to_hash.deep_symbolize_keys.deep_merge(defaults)
-    end
-
     def normalize_hash_arguments(args)
       args.deep_symbolize_keys!
 
diff --git a/spec/lib/gitlab/auth/saml/config_spec.rb b/spec/lib/gitlab/auth/saml/config_spec.rb
index c19171bb6f8fd9ce47499f0c46db0ea98c5b0139..2ecc26f9b9641dd8582308ea3f20b23f908f86c1 100644
--- a/spec/lib/gitlab/auth/saml/config_spec.rb
+++ b/spec/lib/gitlab/auth/saml/config_spec.rb
@@ -19,41 +19,6 @@
     end
   end
 
-  describe '.default_attribute_statements' do
-    it 'includes upstream defaults, nickname and Microsoft values' do
-      expect(described_class.default_attribute_statements).to match_array(
-        {
-          nickname: %w[username nickname],
-          name: [
-            'name',
-            'http://schemas.xmlsoap.org/ws/2005/05/identity/claims/name',
-            'http://schemas.microsoft.com/ws/2008/06/identity/claims/name'
-          ],
-          email: [
-            'email',
-            'mail',
-            'http://schemas.xmlsoap.org/ws/2005/05/identity/claims/emailaddress',
-            'http://schemas.microsoft.com/ws/2008/06/identity/claims/emailaddress'
-          ],
-          first_name: [
-            'first_name',
-            'firstname',
-            'firstName',
-            'http://schemas.xmlsoap.org/ws/2005/05/identity/claims/givenname',
-            'http://schemas.microsoft.com/ws/2008/06/identity/claims/givenname'
-          ],
-          last_name: [
-            'last_name',
-            'lastname',
-            'lastName',
-            'http://schemas.xmlsoap.org/ws/2005/05/identity/claims/surname',
-            'http://schemas.microsoft.com/ws/2008/06/identity/claims/surname'
-          ]
-        }
-      )
-    end
-  end
-
   describe '#external_groups' do
     let(:config_1) { described_class.new('saml1') }
 
diff --git a/spec/lib/gitlab/omniauth_initializer_spec.rb b/spec/lib/gitlab/omniauth_initializer_spec.rb
index e12c0f4e78b0e845a67d6b5888f48c44143cdfe9..9b46b8eccc8b57a309aa67b5ad1151150255b1b5 100644
--- a/spec/lib/gitlab/omniauth_initializer_spec.rb
+++ b/spec/lib/gitlab/omniauth_initializer_spec.rb
@@ -2,9 +2,7 @@
 
 require 'spec_helper'
 
-RSpec.describe Gitlab::OmniauthInitializer, feature_category: :system_access do
-  include LoginHelpers
-
+RSpec.describe Gitlab::OmniauthInitializer do
   let(:devise_config) { class_double(Devise) }
 
   subject(:initializer) { described_class.new(devise_config) }
@@ -226,119 +224,6 @@
       subject.execute([shibboleth_config])
     end
 
-    context 'when SAML providers are configured' do
-      it 'configures default args for a single SAML provider' do
-        stub_omniauth_config(providers: [{ name: 'saml', args: { idp_sso_service_url: 'https://saml.example.com' } }])
-
-        expect(devise_config).to receive(:omniauth).with(
-          :saml,
-          {
-            idp_sso_service_url: 'https://saml.example.com',
-            attribute_statements: ::Gitlab::Auth::Saml::Config.default_attribute_statements
-          }
-        )
-
-        initializer.execute(Gitlab.config.omniauth.providers)
-      end
-
-      context 'when configuration provides matching keys' do
-        before do
-          stub_omniauth_config(
-            providers: [
-              {
-                name: 'saml',
-                args: { idp_sso_service_url: 'https://saml.example.com', attribute_statements: { email: ['custom_attr'] } }
-              }
-            ]
-          )
-        end
-
-        it 'merges arguments with user configuration preference' do
-          expect(devise_config).to receive(:omniauth).with(
-            :saml,
-            {
-              idp_sso_service_url: 'https://saml.example.com',
-              attribute_statements: ::Gitlab::Auth::Saml::Config.default_attribute_statements
-                                                                .merge({ email: ['custom_attr'] })
-            }
-          )
-
-          initializer.execute(Gitlab.config.omniauth.providers)
-        end
-
-        it 'merges arguments with defaults preference when invert_omniauth_args_merging is not enabled' do
-          stub_feature_flags(invert_omniauth_args_merging: false)
-
-          expect(devise_config).to receive(:omniauth).with(
-            :saml,
-            {
-              idp_sso_service_url: 'https://saml.example.com',
-              attribute_statements: ::Gitlab::Auth::Saml::Config.default_attribute_statements
-            }
-          )
-
-          initializer.execute(Gitlab.config.omniauth.providers)
-        end
-      end
-
-      it 'configures defaults args for multiple SAML providers' do
-        stub_omniauth_config(
-          providers: [
-            { name: 'saml', args: { idp_sso_service_url: 'https://saml.example.com' } },
-            {
-              name: 'saml2',
-              args: { strategy_class: 'OmniAuth::Strategies::SAML', idp_sso_service_url: 'https://saml2.example.com' }
-            }
-          ]
-        )
-
-        expect(devise_config).to receive(:omniauth).with(
-          :saml,
-          {
-            idp_sso_service_url: 'https://saml.example.com',
-            attribute_statements: ::Gitlab::Auth::Saml::Config.default_attribute_statements
-          }
-        )
-        expect(devise_config).to receive(:omniauth).with(
-          :saml2,
-          {
-            idp_sso_service_url: 'https://saml2.example.com',
-            strategy_class: OmniAuth::Strategies::SAML,
-            attribute_statements: ::Gitlab::Auth::Saml::Config.default_attribute_statements
-          }
-        )
-
-        initializer.execute(Gitlab.config.omniauth.providers)
-      end
-
-      it 'merges arguments with user configuration preference for custom SAML provider' do
-        stub_omniauth_config(
-          providers: [
-            {
-              name: 'custom_saml',
-              args: {
-                strategy_class: 'OmniAuth::Strategies::SAML',
-                idp_sso_service_url: 'https://saml2.example.com',
-                attribute_statements: { email: ['custom_attr'] }
-              }
-            }
-          ]
-        )
-
-        expect(devise_config).to receive(:omniauth).with(
-          :custom_saml,
-          {
-            idp_sso_service_url: 'https://saml2.example.com',
-            strategy_class: OmniAuth::Strategies::SAML,
-            attribute_statements: ::Gitlab::Auth::Saml::Config.default_attribute_statements
-                                                              .merge({ email: ['custom_attr'] })
-          }
-        )
-
-        initializer.execute(Gitlab.config.omniauth.providers)
-      end
-    end
-
     it 'configures defaults for google_oauth2' do
       google_config = {
         'name' => 'google_oauth2',