ScrambledClientside VAC seems to have been implemented for Linux CSGO June this year, the 4 month old readme for cathook boasts about needing to be manually vacbanned. Was Linux TF2 VAC implemented in the last 4 months?
If so then I'm sorry, I don't keep that up to date on these things.
VAC always existed on Linux. Not sure where you got the information about CSGO, nor do I know what you mean by CSGO or TF2 VAC "implementations" in the first place.
VAC is implemented in Steam itself, not any game client.
nullifiedcat is just complaining about his personal accounts getting manually banned and spreading lies about VAC to make his cheat look better/more usable.