This is the way I see it as well. I breed several different breeds. Of course none of the others go through the scrutiny of having the hatcheries selling mutts, but that doesn't pertain IMO to standard bred birds. If I breed a BBRed Cubalaya to another BBRed Cubalaya, I still get BBRed Cubalayas, but the quality ranges. Now according to some people, if I breed the same way but breed two Wheaten Ameraucanas together, and a bird comes out with a little darker shade over the body... It is not an ameraucana? I believe it to be an Ameraucana still, just lacking like any other breed can in the color of the bird. I'm not saying that a bird that has green legs, lays green eggs, and has Partridge color pattern is any kind of Ameraucana, but things tend to be blown out of proportions.
Of course everyone has thier own opinion, and this is just mine.
I like the penguin analogy, perfect example.