Head dog has the advantage for that reason and the fact that the other dog's head is where its weapons are.
He who controls the head controls = how much he gets bit ...
Meanwhile, he whose head is controlLED = he who is ineffective.
The only other place you can bite, and not control the head, is deep in the throat.
From a tactical standpoint, breeding for dogs that control the head = breeding dogs that control the deal.
Jack