Apparently this is a big moment, as Just Communication just started up.
Quatre’s line of thought very obviously does NOT cross Trowa’s mind. What he is thinking is not “OH BOY NEW FRIEND,” it’s “Well, his mobile suit is just as powerful as mine, I’ve no bullets left, and he has forty friends pointing beam weapons at me. He probably wants my suit intact, so he’s stopping the fight because he knows I know there’s no getting out of this. Welp, better face the music.” And he emerges with his hands up.
And then this weird ass kid (Quatre could never be mistaken for being an adult) says these… nice things.
Trowa has no frame of reference for this, and you can tell by the fact that he keeps his hands up even after Quatre says he can put them down. You can’t see it, but I’m going to bet that Trowa’s face in his mind’s eye is quite “buuuuuuuh?”