[GrandComplete]

Yeah count me in on not getting on why people keep saying Geiz flip flopping is inconsistant. Early on we establish Tsukoyomi being able to get Geiz to relent even while being his stubborn self. So what originally got him to back down was that. But he hasn't formed a meaningful bond with Sougo which is why he was so hostile in the beginning. But as the show keeps going his constant threats were seen more or less to keep a status quo and you can see that even he clearly dosen't believe in it anymore.But Geiz constant pressure of future events feels as if he has no choice but to keep up. Which is why when Sougo and Geiz were reminded by Tsukoyomi about changing destiny and not going through with "final battle" in episode 28 that Geiz drops his constant threats.
It's this bond that allows Geiz to be more wary of White Woz as the old Geiz would've taken the powers of Revive without question. As well as for both of them to come to understanding so quickly once Hiryu reseted the world and history.(It also an indication of Sougo growth but that whole nother tangent)