It’s not a gimmick feature. It’s just the “user” is always, inherently, in “control” of the kernel itself when it comes to Linux. That’s not true with NT or Darwin. You (a 3rd party) can always verify NT or Darwin’s “integrity” by checking it’s cryptographically signed by Microsoft or Apple. Other than assuming that Valve (or Sony, Nintendo, Debian, SUSE, RedHat, etc) is the “trusted kernel” for your game, you can’t do that with Linux. And the moment you say “My application only runs on Kernels signed by {insert organization}, are you really “Linux”?