Yes and no. For any given breed, one color earlobe is considered correct and one is considered wrong. But sometimes a chicken will have the "wrong" ear color for their breed. So they definitely exist, but according to the breed standard they are not correct. For that study, when I go skim-read the text, they had quite a few with white earlobes, even though that is "wrong" for the breed. Earlobe color has no effect on egglaying ability, so it might get ignored in a commercial flock, which is probably what happened here.