Raphael is more inclined to nest on certain angels than others - and while it's true that Samandriel is younger, his vessel is also younger and weaker than that of the other angels as well, and that provokes Raphael to be protective as well. Especially in these situations.

"It could be, but no one says we have to go through first." He was fully planning on getting others to exit first, so that they had some idea of what the end was.