The idea is that it would require a verified hypervisor, and verified operating system for the game, but you could still at the same time be running an unverified operating system with unverified software. The trusted and untrusted software has to be properly sandboxed from one another. The computer does not need to be locked down so you can't run other hypervisors, it just would require that the anticheat can't prove that it's running on a trusted one when it isn't.

The security of PCs is still poor. Even if you had every available security feature right now it's not enough for the game to be safe. We still need to wait for PCs to catch up with the state of the art, then we have to wait 5+ years for devices to make it into the wild to have a big enough market share to make targeting them to be commercially viable.