Nah, I don't think that at all. Still of course it's just one of those many things that you can read all sorts of things into. I just think that Jack probably does it to everyone, and it's a way of intimidating people and showing your power over them. Then again I've never seen the Jack/Gwen thing, so when I saw that scene I didn't read it that way, but I'm sure it's a favourite scene for those into the J/G.