As I said, I doubt anyone has the time to be that specific, and most of the ones I've seen involving the head were fatal, often DRT.
The curb makes a huge difference. It is a non-compressible surface, and when the stomping is done (as it generally is) on the edge of the curb or on the part of the limb with a gap behind it, it is extremely destructive. Open fractures are common.
Do I need one? I'm asking you to provide something other than unsupported opinion for YOUR theory. Unsupported, so that ties in with the curb stomping...
If I was to guess, I would say it's because facial injuries have a massive "ick" factor, and people want to avoid them for that reason. And perhaps also because if you tried to fish hook me, I'd certainly do my level best to bite your finger right off. Which is also something sporting associations would prefer to avoid. But those are just guesses, mind you.
You are free to believe whatever you like. But unsupported opinion, even from an expert, is still unsupported opinion.
So are you retracting your statement that these injuries are "well documented in trauma medicine" yet? Because that doesn't seem to be the case. Standing behind one claim which has been shown to be false does not help your other unsupported claim...