It also boils down to a simple fact that on certain shifts at WM there are not competent employees in the sporting goods department. I encountered this once when trying to buy some rounds to take to the range. The dude didn't know a .22LR from a 9mm. Slight exaggeration but you get my point.
So walmart can't afford basic reading skills? Its not like the packages are unmarked or the ammo comes in a big bin as nails do and one has to scoop them out into a brown bag, weight them and know what the bullets look like.