I suspect that the product info on that model is a typo, and should read built-in.
FWIW, we had a double built-under and although the main oven is smaller, we didn't find it too much of a limitation: for us, it was worth losing a bit of oven space in order to get a separate grill. This is, though, a compromise I'd only make in a small kitchen - a bigger double at eye level is definitely preferable.