On his own, isn't Jensen a little more shy and quiet?

He is. Jared does tend to bring him out of his shell a little bit, because Jared obviously does not have a shy bone in his body.

I also remember Jensen saying something about liking to do interviews and such with Jared because if it starts to make him too uncomfortable, Jared will jump in and take the spotlight onto himself for a bit until Jensen is ready to jump back in.