TB - thanks a ton for continuing this - I don't want to delve too far into this discussion on this thread, mainly because the bat-engineering discussion is excellent and I'd love to see it remain on track.
However...
The two photos which I put together above are on vastly different pitches and therefore approaches to hitting them. What you cited regarding the X and Y axis, the bat in relation to the hands, etc are pretty much spot on and I doubt you'd get much debate there. But what is driving the differences is the pitch location. As Dunnin suggested, the pitch is significantly higher in the baseball photo than the one with my daughter and based on the position of the outbound baseball, he was still under it a bit. Kudos to the hitting coach with this boy - he has a very nice looking swing with good extension and a very firm front side. Note that he is exhibiting just a bit of tilt, but his weight is likely 99% against his front foot. Nice photo too.
As to the mechanics of it though, on a high pitch in general the swing necessarily flattens out and the bat barrel remains virtually parallel to the ground - pretty much even with the hands. On a lower pitch, thigh-high, the hands are almost always above the barrel. Imagine if one were to hit a ball that were knee-high. Could you imagine trying to keep the hands even with the barrel? You would have to drop to your knees in order to keep the hands parallel...
Remember, we're actually working on a premise that there are two different planes acting in concert together. The plane of the ground sets up the concept of hands being above the barrel of the bat on a "fat" middle-in belt high fastball. In fact, if you reconsider and utilize the swing plane... voila'! The hand's ARE on the same plane as the bat if the ball were a high pitch as you suggest where the swing plane is closely matched to the ground plane.
I have to admit that my initial thought about the comment of a too-long bat was somewhat defensive, but as I step back and stay objective, I do understand what you're saying. I've done a fair amount of study on the science of hitting and reviewed literally hundreds of video clips over the years of high-level hitters,. So that being said, I am well aware of the lag you describe. I wish I had a split-screen view I could load to show my DD's bat from more of a 90* side-view like the baseball hitter is so that you could look at the hand/barrel proximity from a y-axis perspective. (The barrel actually lags very little) It's funny though - as I go back and look at this photo again, one thing I am seeing is that if we consider the x-axis as correctly parallel to her shoulders and we utilize a swing plane parallel to that axis, I actually see the barrel appearing to be slightly ABOVE her hands - something I had not noticed previously. I can't say if that's the result of the camera angle or if it's actually occurring, but I think I do see it. In any case, the optimal slight upward swing plane is there as it invariably is with her on the mid-lower pitches and she replicates it constantly.
I'd love to continue this discussion, but as I said, I'd feel bad if this string took a turn away from the very excellent subject it has been n up to this point. Maybe a different thread, or via IM...?
Again, thanks a ton to TB and Dunnin for your very excellent input! You are part of the reason HB is such a terrific resource and forum!!!
It works! 
just click the picture below to see the slideshow . . .
