Perhaps *original* bettas that haven't been bred to be so colorful and such. I'd be kinda wary that they were pulled from the rice patties they live in
"Wild-type" males are exactly what they sound like; they are close to one of the origional wild betta species, hence the lack of large fins, which were pretty much bred (as were the various mutations of the fins) by fanciers for more attractive fish.
I think they are just plakats and the store owner doesn't know the word for short tail bettas... So thinking of the best thing, he went for "wild" bettas.