This is a detail that I noted, and just called plot at first glance, which it is.
Mihawk postpones the little clash with vista:
Literally 5 pages after, Squardo betrays WB:
Everyone stops fighting to acknowledge this, it all goes quite, WB pirates are shocked, the ones in on this aren't however, and have stern expressions:
I called this just plot because if Mihawk didn't postpone, we couldn't get Vistas reaction like we did, because he'd be too busy trying to fight Mihawk, this is would obviously shock him so much to the point where he might even just get killed by Mihawk for being distracted by what's just happened.
I'm gonna just throw this out there and say Mihawk saw this occur beforehand with FS and that's why he asked vista to postpone with such perfect timing. It makes sense.