I have two that lean and two that don't. My guys, though, don't just lean for the sake of leaning. Generally, it starts as me petting them and they lean into it. One of the leaners is very insecure during storms, fireworks, etc, and will stand next to me in all his quivering glory during one of those events. On occasions, he leans then, too.

I can see where it could be viewed as dominant behavior, but I don't feel it applies in our circumstances.