Revelations from Patch 5.3

[Rannie]

but Elidibus

did not become a primal. the one we knew since 2.1 IS a primal. He is no real Ascian. the original one was sacrificed for Zodiark's summoning. it is questionable if "our" Elidibus ever witnessed Zodiark in action.

In the English version of of the cutscene in amaurot

Y'shtola clearly states that she knows he sacrificed himself to become the heart of Zodiak but and I quote, "How you became separated from Him isn't clear. But if you are a fragment of His being, it stands to reason that the world's salvation drives you." And he acknowledges it.

Meaning

he wasn't just created from nothing but was created as himself but in a primal form and seeing as how he has the original memories Elidibus as well. Granted those memories have been eroding over time due to him trying to fulfill his objective as a primal but is most likely still Elidibus the true one or a small part. However, they others still considered him unsundered most likely as they did not realize exactly what happened to him if he can even be considered aundered due to being said primal.