Quote Originally Posted by Lethallin View Post
It's to prevent spoilers. Which is really unnecessary, but that's almost certainly the reason.
I don't really think the Extreme mode primals count as spoilers though. Same with the various hard mode mode dungeons to unlock the 50 roulette. Or even with this new patch with the new Expert roulette it had the "???" also even though the patch notes already told you specifically where to go to unlock those dungeons (Ampador) or strongly hinted at it being unlocked over the course of the main story (Antitower). So the "spoilers" thing doesn't really fly in my opinion.