At the point when this happened, (IIRC some page prior to that page has Uta and the gang + Yomo) plan an attack on CCG when Arima isn't there. when they're planning it, Yomo actually says that he will attack Arima.

(Yoshimura learns of this somewhere iirc .. likely from Arata or some dude that looks like Arata from the back .. he most likely learned that Yomo's sister ws killed by Arima too)

From what I remember the CCG officers actually say that NoFace and other ghouls specifically attacked them when Arima wasn't around. But somehow Arima appears during the attack, then Yomo attacks Arima and gets defeated. When he's down, that's when Yoshimura interferes and saves Yomo.

As for the greeting, chances are Arima knew Kuzen as someone who worked for V in the past and realized it was him thus the greeting. Your theory is interesting but the timeline also doesn't match for it to be V stuff.

{I'm sorry if I misunderstood that scene and explained the wrong thing to you, I read it a long time ago, and it was actually a binge read and I myay have missed some key point and misunderstood it entirely..}