The problem is since Valve and Proton made windows games viable for Linux and the Steam Deck, most of that anti-cheat vermin does NOT work under Linux. Even if it did, if you run Linux, you likely take some objection to someone wanting to add kernel modules of unknown and/or ill repute to your pretty open-source kernel.
Valve knows this, kernel-level anti-cheat is simply not practical for use with Linux as a consideration. Most game companies care zero for Linux in the first place, which means for us, we just end up inadvertently boycotting those games and bad-mouthing them regardless, but hey, it's only 1%.
I think the end goal of Valve is to support anticheats in Linux. But they want the Kernel to provide an API for it, so you don't need to run the anticheat like a driver.
But will a canned, defined api ever be good enough? As soon as someone paints a border, someone will step over it. It's the reason security products in windoze as well as anti-cheats require kernel-level access, and why outages like the crowdstrike one a few months ago occur and why microsoft lets it (for now).
It's an arms race, and no api will ever be good enough to keep a miscreant from working against logical choices. If I have to play a game that I have to assume someone is cheating, I really don't want to play that game, or at least with others of dubious reputation. This is why I run my own server for games I like to play with others I trust.
If someone wants to play competitively publicly with anti-cheats, they should opt-in to do so, but I'd like the option to not, and simply play local or private instances with my own general TOS. If diplomacy fails, a ban option for the server.
Valve knows this, kernel-level anti-cheat is simply not practical for use with Linux as a consideration. Most game companies care zero for Linux in the first place, which means for us, we just end up inadvertently boycotting those games and bad-mouthing them regardless, but hey, it's only 1%.