That's a problem with all the "magic" operators (::`->, ::_indices, etc). If we can come up with a better syntax it shouldn't be very hard to keep them accessible. I don't see any point with that a parent class can keep them inaccessible from the inheriting class, if there ever was such an intention.
A point in case is also that those functions aren't quite the same thing as the operators whose names they use. It shows for instance in the intentionally undocumented indexing type argument to ::`->, ::`->=, ::_indices and ::_values. With that argument, it's possible to access static class members and members of inheriting classes. This indexing type argument isn't a good solution (which is why it has remained undocumented); I think there ought to be a separate function for each indexing type instead. I.e. ::`-> should be broken up into at least four separate indexing functions, etc.