Somehow "the queen is actually a prince in disguise" is so much less interesting than "the prince is actually a princess in disguise".
My personal issue is that the latter sets up a fun GL romance, and the former just teases GL while actually being just another het romance.
Nominally they're just the same idea from different sides, and yet...
Honestly if the "queen is actually a prince" story was BL I would have a lot more respect for it.