Well, while looking up their full grown size (0.8 - 1.0") I discovered that it appears the tank at the store was mis-labeled and these are actually Corydoras pygmaeus...but I'm still happy because those were the 2 types of dwarf cory I was looking for. So mislabeled or not, I'm happy with my teeny new additions to the tank!
And it sounds like these guys stay a little smaller than the hastatus anyway, which is good because the tank is only 5g and already has a Betta and 2 otos in it.