An anti-cheat is one of the few areas that truly would ruin its security by going OSS. A cheater can quickly enumerate every method the AC uses to detect cheats, then they know EXACTLY which goalpost to kick into, per-se. 85% of Vanguard's effectiveness is their CONFUSING ban protocols, whether that's delaying a ban to confuse someone testing what's bannable, not divulging details about what avenues are tested, constant updates that aren't specified anywhere, etc.
Case in point, even in CSGO: Just changing the offsets of some game values will break some cheats for several days.
Obscurity can be a layer, but it can't be the only layer, and in general systems (such as web servers) need to be designed to withstand full-knowledge attacks. That isn't likely to be possible when it comes to anti-cheat, so obscurity plays a larger role.
State owned is problematic, I'm not in disagreement with you. But so is corporate owned. I'd like to see an industry standard anti-cheat root-kit developed as a publicly reviewable open source project at the very least.