It means more than just that. There are multiple unique modes of minor, and advanced music exams will also bust out enharmonic requirements, playing in thirds and other things that requires very extensive practice.

Source: I’ve done several of these exams.

In this context, where the article speaks of "all 24 keys", it most certainly doesn't.

Usually for each minor key there are three minor modes they can request. That would be 48 different scales as a typical minimum. (not including other requests that are typically made of scale playing in these exams)