Haha, bingo, you are the first guy who aware a lot about the difference on that endoskull after modded......as you say, the teeth size on lower jaw have been adjusted (the teeth on upper jaw also adjusted a bit actually)........I have try to widened the cheekbone by add a piece of plastic board under it, but I remove it finally because it look so strange, so I think the shorten teeth on lower jaw and the soft pipe mislead you feel that the jaw widended (the position of the figure when I take photo maybe one of the reason) ........
Wow, yeah it's strange the effect that had, I really did think you had widened the jaw, perhaps by adding to the existing sculpt yourself and repainting the whole thing. A member here did that to a Hot Toys Endoskeleton which he then sold to me some years later.
So, a big improvement, you've greatly reduced the 'goofiness' of the original sculpt. As you admit in another post it's still not all the way there but there's only so much you can do.
It's a real pity Enterbay dropped their plans for an Endo. QC would have been awful most likely but I'm almost certain we would have had a superior sculpt from them.