I like the way Heath bends his knees like that. 
In these pix, you get the opposite effect -- Heath looks much taller, because he is closer to the viewer than Jake:





I don't think Heath is that much closer to the viewer, to account for him looking taller than Jake. Let's see, look at the third picture -- maybe those shoes of Heath's have thicker soles. Or maybe he is taller at the shoulders, and a shorter neck, then Jake has longer neck, plus, as you say, the hair and all, so they end up looking quite close at the top of the head. But in BBM, kissing and all, Jack had to look up every so slilghtly to meet Ennis's eyes.
I can't believe I'm sitting here talking about an inch here, an inche there... (No, I'm not talking about those inches! I was not even thinking about that, until your sex-obsessed minds started me thinking of that...)
kathy