My understanding is petting on top of the head, or leaning over the dog, is a dominant position. Dogs approach each other from the side, not head on and the head and body over the back is a dominance thing. IMO, this is a DOG thing and not a BREED thing.
I'm not a big believer in the dog/people dominance theory. I think they know we aren't dogs. But I have seen dogs react differently to people petting them on the top of the head vs the chest area. It might be excitement too. Their hands are closer to his head, more visual, etc and he might just be trying to play.
~The strength of one's opinion should not exceed their knowledge on the matter~