Dear IT admin 92923
Thank you for posting in the Microsoft community.
Regarding your question this registry entry is no longer valid in WINDOWS 10 High and WINDOWS 11 under testing.
Most of the current programs no longer work in the new UI, which may be related to Microsoft's change to the Easy Access logic in the login options.
For this issue, you are correct in your conclusion that the only way to prevent the use of Easy Access at this time is by disabling the entire process. Of course for your group policy and registry function issue is beyond the scope of forum support.
You can submit your question at the following site. This is a question community for professional enterprise IT staff or advanced users.
https://learn.microsoft.com/en-us/answers/tags/380/windows-10-security
Best Wish
Shawn Z | Microsoft Community Support Specialist