Arthur's reasoning is that it's also rude to have the bags just littering the hallway, he can duck outside to say hello later. Maybe much later. But Arthur leaves the door open, so he can hear snitches of conversation. Percy is handling everything beautifully. You wouldn't know it, looking at him, that he was flipping out about this a few days before. Arthur lacks his grace. He lacks everything that Percy has, except maybe good judgment.
Eames is back with M16 now. Arthur hasn't looked him up, but he knows enough about that world to know that maybe Eames wants to stay there.
Eames told him in Prague, that no one called him Daniel. Except apparently Dr. Stephen Miles. And Percy's brother has made quite an impression on Daniel. That is, Eames.
"Oh, I know." says Percy, the smug bastard. "Only because that impression cuts both ways." And then he says, "Arthur Ryan, at least come out here and say hello." Percy middle-names him very sparingly, but it gets him every time. Arthur slinks out from behind the door.
"...Professor."
Eames is practically sprinting away, taking the stairs two at a time. Percy gives him a look.
"And Mr. Eames too, Arthur. Havana has really done a number on your manners."
"Percival -"
"Arthur."
Percy and Miles probably have traded extensive notes about raising boys. Arthur hates them both, but if he stays here, Percival's just going to hark on about it until Arthur actually goes up there and says...something. He sucks in a deep breath, and then he heads for the stairs.