The angel Jace met didn't have any reason to pretend to be anything but what it really was either.

Gabriel swears. "Alec, get back here! If I wanted you in the lake, I would have put you in it!"

Then he folds his arms across his chest to give Jace an even look. "More like concerned you might decide to do something that would get you put in the psyche ward of a Mundane hospital so they could keep an eye on you for a few days."