Text book perfect positioning at foot strike. I can definitely see how that late, explosive hip rotation could actually aid some pitchers reach the position I see above. I definitely don't teach it out of my pitchers (and most do it). I just don't teach them to do it for the purposes of the move itself. I think what I resist is the notion that holding the hips closed until late in the motion adds anything to the desired tension that is the rsult of good hip/shoulder separation. I believe the tension is 100% a result of the separation itself and not a product of the method by which it is attained. As an analogy, if I pul a rubberband back 6 inches and let it fly, I won't get any extra elasticity or energy from tension if I pull it back quickly and let go compared to slowly pulling it back. The energy gained isn't from pulling it back, but rather from it having been pulled back.
By the way, we all work very hard to get our pitchers where your kid is at foot strike.