It might be important to remember that both Lahabrea and Elidibus are said to be "of this world," which likely means they're Source native, so not from the Thirteenth. This matters more for Lahabrea than Elidibus since you put the latter aside.

As for what the Thirteenth world is an homage to, feh feh, still plenty of time to speculate before we get any real answers I bet! With 4.0 rife with rumblings of the Corpse Brigade I'm always eager to retrod Ivalice's familiar plains