I did not know that. Although I would say that my rooster falls into that minority (he doesn't have the spike at the top of his comb, and his wattles are just slightly asymmetrical). However, I do not know about my hens. It may be that some of them have a nice back but maybe I can post pics sometime for you guys to see since I know nothing about that. I know that 4/6 of the hens have the spike at the top of their comb, one has an underbite and is smaller than the rest, and they all seem to be pretty dark in coloring. Probably not the greatest gene pool but they are very docile, friendly, and adventerous.
If you're not planning to breed for show or sales it's not a problem. But if you plan on breeding for show, 4H, or selling hatching eggs/chicks, then flaws would be a problem. From what I understand on this thread is that Doms sometimes don't have the leader (spike) whether it never grew, got chewed off, or frostbite, whatever, and for SOP it seems to be a requirement. It's mind-boggling how many 100's of birds breeders must cull to get just a few good stock to perpetuate. And as customers we have to realize not every bird we buy from a show breeder, backyard breeder, or hatchery is going to be perfect breeder stock. Two beautiful show birds might produce as many dud chicks as good chicks. Thus, you see the term "cull heavily" when breeding for SOP. Because I don't show or breed I don't mind a "cull" as long as its breed is recognizable and has no gross malformations. My priority after an obviously healthy bird is that it has the temperament and qualities I need in my backyard flock. There are several SOP qualities I love about Doms but in the end for me I want the sweet temperament, lightweight bird, that doesn't exhaust herself laying her pretty brown medium eggs I'm a sucker for making a pet out of any animal we add to the yard and Dom has been a most fun bird for us.