all oda had to do to make that panel time be coherent with the decision of staying in wano was to never have yamato mention the intention of joining the crew. this is what a good writer does. he leaves the door open. instead he kept having her say she assumed to join, told kaido she was gonna go out in the sea with luffy, presented to the crew as one of them, and got told to not fight an admiral because of the fact she was leaving.
no matter how much you twist it, oda never once had yamato question her future role. so her changing mind at the last second is bad storytelling, whatever you like or hate the character.
the admiral scene is bad, but i can accept it because of the purpose the writer is telling the scene has. i can accept sukiyaki doing the opposite of what he said 2 chapters before because i accept that having the emotional reveal is good.
with yamato staying there is no purpose behind the twist. is just there for the sake of making a twist out of nowhere, to say "bet you didn't see this coming".
duh, of course i can't see a twist if you just straight up lie, instead of leaving the door open for many different outcomes.