Kernel anti-cheat systems are currently the bane of Linux/Steam Deck gaming, haven’t actually proven to be effective at stopping cheaters (see Valorant for an example), and lead to various security concerns from giving 3rd parties full access to your machine to being used to install ransomware and malware.
Windows tried to restrict kernel access years ago, but backed down under pressure from various companies. However Crowdstrike’s outages have shown the sever consequences of leaving kernel access open, and we might finally see kernel access to be cut off.
Client side anti-cheat is inherently flawed. These games are asking an untrusted computer whether it is cheating. That’s like asking a known liar whether they’re lying at that moment. The one way to make it harder for the computer to “lie” is by increasing the permissions the AC has, which comes at the cost of privacy for people with the game, and security for every Windows user (not just the ones with a certain game installed).
Client side anti-cheat can be poked and investigated locally, with no restrictions. All it takes a skilled enough cheater is time, and they will bypass it. The only way to test server side anti-cheat is by hopping in the game, trying to learn how it works, and trying to bypass it. That is a much more time consuming and expensive process.