Could well be both.
But note that you're talking on a group that's mostly American, and we're used to low platforms. Of course, American railroads try to avoid curved platforms anyway, but you often see them on models. With high platforms, you either have to make them straight or, if you're using the curves that model, uh, railways typically have, you need to allow plenty of clearance. At least that's not a problem with the American prototype.
"Mind the gap", indeed!