I too was wondering the source of this info too sounds a little off to me.
Most of our American class of chickens were developed from the surrounding/area breeds/types of chickens in the local regions during that time and there are a lot that have Gamefowl in their backgrounds. I don't know of any of the Amer. class that have any white-face black spanish in them(not as one of the original/dominant influentual breeds that is)?
I would dare to say that the white faced black is a breed just as the leghorns and a lot of today's known breeds were developed from 'dunghill gamefowl' centuries ago.
Jeff