As I see it they offer one. Stretching it, two with the 3G, but the wifi will allow for the same capabilities when in range. Different SKUs or not I think you understood exactly what the poster meant. It's "the same device with different storage capabilities + the choice of wireless". To Apple they are of course different models, they have to design, plan for and produce it, but the customer will see an "iPad", which can in turn have 16-64GB flash + 3G.
In other words 'Apple doesn't differentiate' really means 'Apple doesn't differentiate in the way I want them to'. One might as well say there's 1 model of MBA and say 'the differences between them don't count (for some arbitrary reason)'.
I understood exactly what the poster meant, they meant to cloud the issue and cast FUD.