Document collections are showing misleading "last updated" data for mainstream content

app/presenters/document_collection_presenter.rb

@@ -41,7 +41,7 @@ def group_document_links(group, group_index)
           },
         },
         metadata: {
-          public_updated_at: link["public_updated_at"]&.then { |time| Time.zone.parse(time) },
+          public_updated_at: group_document_link_public_updated_at(link),
           document_type: I18n.t(
             "content_item.schema_name.#{link['document_type']}",
             count: 1,
@@ -69,6 +69,22 @@ def taxonomy_topic_email_override_base_path
 
 private
 
+  def group_document_link_public_updated_at(link)
+    disallowed_document_types = %w[answer
+                                   completed_transaction
+                                   guide
+                                   help_page
+                                   local_transaction
+                                   place
+                                   simple_smart_answer
+                                   transaction
+                                   smart_answer]
+
+    return nil if disallowed_document_types.include?(link["document_type"])
+
+    link["public_updated_at"]&.then { |time| Time.zone.parse(time) }
+  end
+
   def group_documents(group)
     group["documents"].map { |id| documents_hash[id] }.compact
   end

test/presenters/document_collection_presenter_test.rb

@@ -103,6 +103,34 @@ class PresentedDocumentCollection < TestCase
 
       assert_nil grouped.first[:metadata][:public_updated_at]
     end
+
+    test "it returns nil if specfic document_type is in the disallowed_document_types list" do
+      schema_data = schema_item
+
+      disallowed_document_types = %w[answer
+                                     completed_transaction
+                                     guide
+                                     help_page
+                                     local_transaction
+                                     place
+                                     simple_smart_answer
+                                     transaction
+                                     smart_answer]
+
+      disallowed_document_types.each do |document_type|
+        document = schema_data["links"]["documents"].first
+        document["document_type"] = document_type
+
+        grouped = present_example(schema_data).group_document_links(
+          { "documents" => [document["content_id"]] },
+          0,
+        )
+
+        public_updated_at = grouped[0][:metadata][:public_updated_at]
+
+        assert_equal nil, public_updated_at
+      end
+    end
   end
 
   class GroupWithMissingDocument < TestCase