I’m not a Lab expert by any means, but I have heard very recently somewhere that Yellow Labs used to be considered inferior(ie not up to breed stds), and were actually plucked from the litters by hunters and not bred. And they became isolated for a while or some such...I think I have that right. If not, hopefully someone with more specific breed knowledge than I have clarify. Perhaps distinguishing them recalls historical views of various types of Labs. Sounds plausible anyway.:)
Yellow Labs have always been favored by the show (conformation) breeders. The color first appeared in 1899, so it's not like it's anything new. It's basically a Black Lab with the gene for coat color turned off. The chocolate color is a separate recessive gene for the basic coat and skin color.
My young Black Lab is "tri-factored" - she carries the yellow and the chocolate genes, disguised by the dominant Black gene. So depending on who she is bred to, she will throw 50% black and 50% yellow (if bred to a yellow Lab), 50% black and 50% chocolate (if bred to a choc), or all black if bred to a black dog with no recessive factor. If you breed her to a yellow- or choc- factored dog, things get more complicated, but basically you'd get 25% pure black, 25% black with the yellow factor (or chocolate), and 25% yellow or chocolate. And if she were bred to another tri-factor dog, you'd get 9/16 Black, 1/4 Yellow, and 3/16 Choc. But I wouldn't do that because of the Danger of Dudleys.
The show breeders did not breed Chocolates for a long time, because of the danger of accidentally introducing a "Dudley" (a Chocolate lab with the gene for yellow coat color - has a pink nose and eye rims) into their yellow lines. They are breeding them now, but because the overwhelming majority of chocolates were field dogs and not show dogs, they got a reputation for being hyper and crazy. Now that show breeders are getting chocs, their dogs are as mellow and placid as most of the show dogs.