Is there a facility, either planned or available, to prevent some ambiguous and/or overlapping tags from being used. See, for example, this discussion Tag overlap: Oracle APEX and APEX VisualForce.
I think that apex could be safely banned, because, for instance, the question Oracle APEX: popup menu before editing had apex, while the better fit would be to have oracle-apex on it, and you could understand neither from initial tags nor from the title what this question is about unitl you follow it and read the question.
apex neither adds anyting useful to the question, nor does it remove the ambiguity. I would get rid of it and retag existing questions having apex to have oracle-apex.