ARK uses both VAC and BE.
Just for clarification, we do not handle VAC bans at all. VAC bans are 100% handled through Steam/Valve, we do not set heuristics, file reports, or anything like that with regards to VAC; all we do is submit signatures of known cheat applications (which Valve check on their end before doing anything with, so we couldn't submit like.. Internet Explorer as a cheat and get people VAC banned for having IE open).
So whatever it was, it's something that matched Valve's heuristics.
- The Right Hand
Rust used to use VAC, now uses EAC.
And for Rust my source is I was (falsely) VAC banned in like Feb 2014, and they definitely make you install EasyAntiCheat.