He doesn't need to vacate. Why should he? UFC can strip him if they want, why should he vacate? It's like saying "well, we won't force you to pay the speeding ticket but you should, it's a nice thing to do". Would you pay? Fuck no. No enforcement, no action. He owes you nothing. Get it through your head. UFC owes fans things, not the fighters. Fighters are there to get as much out of their contracts as they can, and if that means waiting for UFC to strip you of the belt instead of vacating it, than that's what happens. Unwarranted sense of entitlement here is beyond rampant, what the fuck.