Basically, Yesung only ever came if he said specific phrases like "good boy" or "you did well" or whatever. This time, Yesung came before he even finished his phrase, which means something in Yesung has changed (most likely SOMEONE has affected Yesung enough to change him), hence why old fart-face is pissed.
oh damn, i never realized
that makes sense, thanks for clarifying, I did notice the old man had the same expression at the end of chap29 when vp didn't climax when he praised him
why is that old man mad at vp?