We're getting a "new complementary story" related to the Endwalker MSQ... (Spoilers)

[KageTokage]

Seems like the "ruins beneath the Bounty" Emet-Selch mentioned are the dungeon, so I'm wondering if maybe he told us about those places for a special reason, not just because he thought they were particularly interesting.

Said dungeon is also apparently heavily inspired by the Alzadaal Ruins in FF XI and might end up bearing the same name, so perhaps that's why they didn't want to mention it in advance.

EDIT: I just realized Alzadaal was already referenced in-game with it being the name of the Au Ra leader whose tribe was responsible for founding Radz-at-Han in conjunction with the Arksodara (As per one of the sightseeing logs). That said, it wouldn't surprise me if said ruins were both constructed by and named after that same founding father.