I didn't either until I tried to book a two bedroom lock off so that we would be in the elevator building.
I am not sure if they combine them for handicap accessible when you call, but the website will not let you book a 2 bedroom HA villa. (I did not actually need the accessible villa.)
Even if you could book a 2-br lock-off, that wouldn't guarantee you'd get an elevator building. 5 of the 21 2-br lock-off units are in other buildings, and all are beneath a grand villa.