A/B testing fail?

I installed Windows 10 on a freakin’ iMac and Edge gives me the most up to date experience, including the “rounded edge” tab UX, which in the edge flags is called the “Windows 11” settings.

On a Windows 11 system, this doesn’t appear in //flags and I’m unable to activate this newer UI design.

Wow. This is a UI failure. Clearly some kind of A/B crap but um… why is the “11” UI enabled on a 10 machine and blocked on an 11 machine? How does this kind of failure happen