EnableConvertWarnToBlock will not enable - stays False

We have a GPO applied to Windows 11 Pro machine - fully patched and onboarded to MDE. The GPO enables "EnableConvertWarnToBlock" as follows:

The GPO is applied to the machine and the following registry key is populated:

But when I check the status on the client - it will not enable:

I have enabled troubleshooting mode and disabled tamper protection in case this is blocking but nothing seems to work. Its as if MDAV/MDE is not even looking/reading that registry key.

Anyone else have the same issue or ideas on resolution?