Third part anticheats have more sophisticated ways to detect (and most importantly to prevent) process injection, memory tampering etc. I believe that the vanilla osiris is detected, because many idiots cheat blatently got easily banned by OW then vac just uploads and sigs that dll (then vac banning everyone else used or will use the same dll and/or injector). This will enable you to make a new account with a different Steam ID without breaching FACEITs multi-account policies.

VAC has its reputation for not being so invasive, yet it's effective in catching most kids who download binaries from suspicious websites. If you’re VAC banned in the game you wish to play on FACEIT, you will need to contact one of our Community Support agents in a ticket to deactivate your FACEIT account. VAC came out in the time when people were so conservative about there privacy, nowadays it's no problem (for most people) to install a trojan just to play a fucking video game. You couldnt hit your own foot but somehow every 2nd hit is a headshot. VAC is a user-mode AC that relies on signature detection and it's not invasive as the other 'good' AC. Either your account or one linked to yours (via phone number or library sharing) connected to a VAC-secured server from a computer with cheats on it.

Just out of curiosity why is it undected by VAC and detected by third parties? Is it by design or VAC is not as good as third parties anti-cheats? If so why is that the case? Valve certanly has more resources that anybody else to make the best anti-cheat on the market no?

Faceit anti cheat interferes vac