Magical change of appearance in the lore

[Iscah]

But in that case, your answer for 'how canon you want it to be' can't be 'not', because there's a bunch of things that are first divulged in Hildibrand but then become important later, like Godbert Manderville and the truth about Sil'dih.

Hildibrand is a story set in the canon world of FFXIV, so when it references other parts of the world, it is accurate to them.

That does not mean that Hildibrand is true and canon from the outside looking in.

Godbert and Sil'dih exist whether you have done the Hildibrand quests or not, or even if they were hypothetically wiped from the game entirely.