Well put...though a lot of people do actually know that a "co-dom" in the ball world is actually an incompete dominant gene.
My opinion is that since by far, most keepers/breeders have a very limited scope on genetics, myself included...that incorrect or not, things tend to stick once said over and over. Look at morphs that express hypomelanism as one of their defining traits, yet only ghosts are referred to as hypos.