Are slides safe to use in the closed position?

So I get that the "edge" of the slide floor is better supported by the floor of the TT, where it "drops down", to sit flush. But it would seem to me that the rest of the floor is equally supported, whether it is extended or retracted.

Im not trying to be argumentative... just learning. Because I had never even though to wonder. But, I also don't use it in retracted mode, unless I have to put something in an overhead shelf or something.

Mike