The way the site sets it up, Luke is allowed to be on Ahch-To, but Rey is NOT permitted to stay there.
The site even says that they’re not dissimilar to the puffins that naturally inhabit the Irish island of Skellig Michael, where Rian Johnson filmed the scenes with Rey and Luke.
Luke has creature minions at his disposal on Ahch-To, which are being described as bird-like creatures with razor-sharp teeth that are sort of like Gremlins.
But Rey will have to convince the creatures to let her stay on the island, allegedly so she can train with Luke Skywalker, and part of that process might find her battling a sea creature… if the rumor is to be believed.