When I was growing up, we had a native woods behind our house with wild crabapples. My vague recollection was an average sized fruit tree, rather nondescript white blossoms, and small hard crabapples we used as throwing weapons. I think most of the crabapples sold in nurseries are grafted trees chosen for their beautiful blooms and often purple leaves, much different than what I grew up with. I've been more confused by my search because nurseries simply list them as Malus 'Cultivar' without including the species name. I don't know enough about how grafting might affect naming a plant.
(Correctly posted to the right thread, now, again thanks Lin)