Never looked at it that way. That Leia responds to Ben has annoyed me since childhood. It might have been intended as you say but the rest of the film (and trilogy) implies that Obi-Wan is his real name. Leia refers to him as Obi-Wan so it feels like an inconsistency within the film honestly. No one calls him Ben except Luke who has called him that as long as he's known him.
Anyway, Obi-Wan chose Ben because no one would suspect he was a Jedi with a boring name like that.