As example, FaceIT Anti Cheat only works if Secure Boot is enabled. I guess their argument is that they can ensure you only boot genuine Windows and thus they can better check if you've tampered with anything.
well then thats on me and i misunderstood. I thought that with secure boot enabled a tampered operating would not boot and therefore the anti cheat can expect that if secure boot is enabled the os is legit. but yea if secure boot enrollment can be faked then my point doesn't stand anymore.