The quick glance at what Wei Wuxian is wearing was all he needed to see for him to decide he wanted a different option if one was available. And he most definitely doesn't want to be the only one not wearing anything in the room. Respecting other cultures is important! With a body like his he'd like to show off as little as he can get away with while still getting clean.

"Something... something longer." He pauses, then adds: "Please." He only hopes the other man doesn't take his preference as an insult to his own choice in bathing wear.

Even if he's new, that isn't going to keep him from being embarrassed about being unprepared. He should have asked in advance, and that's on him!