They won't, Windows isn't even compiled with AVX2 extensions on, even though every CPU in the last 10y+ supports it, for the fear of it running on some machine that doesn't have AVX2. The whole "CPU unsupported" thing is from the marketing side, trying to push purchase of new hardware, not from the actual devs.

No, it’s not marketing. A big security feature is VBS which isn’t supported on older CPUs.

Completely baseless assumption. Who told you that?