That is essentially my point. The full existence of a godlike primal's personality should not be "one pre-existing person and a husk".
Previously we were told that Elidibus was able to leave Zodiark, but not the effect on Zodiark, and reducing him to being basically useless is bizarre. (And how were they doing the third round of sacrifices while Zodiark was in useless mode and Elidibus was separate?)
It also makes Elidibus's relationship with the other Ascians even weirder. They keep going on about their one true god, but Elidibus is just there as a slightly annoying colleague.
Also, Elidibus's continued "existence as himself" only hints at Zodiark being a husk if you already believe that the heart directly persists as the personality of the primal. If the heart simply provides the base for a primal mind comprised of many souls, then that heart might be able to be removed from the primal after – and even if that does render the primal dormant, the one person acting as heart could just be a key "cog in the machine" rather than the entire engine.
And also, as I said in my previous post, it's not inconceivable (within the knowledge we held pre-EW) that Elidibus never actually separated from Zodiark at all. Rather, suppose if those arguing groups were all thinking of Elidibus and how he would resolve their argument, they might subconsciously summon (or create) a new primal in the form of Elidibus who is actually not the soul still inside the primal. Or perhaps Zodiark deliberately created him as a copy.
Also, to go back to an earlier statement...
This is where my line of thinking is coming from. A normal primal is "influenced by the desires of their creator" but does not require any one of its summoners to act as a heart. But a much larger, planet-scale primal might need a heart because of its size, in which case the desires of the heart infuse the desires of the primal as a whole – but that still doesn't indicate that the heart becomes the primal as a hypercharged version of themself. If a small "heartless" primal develops its own mind independent of its summoners, why shouldn't a larger primal be the same?
The personality of the heart might form a strong influence on the primal, but that doesn't have to mean directly becoming them.
It's also a matter of the language they use. The Ascians created Zodiark. They did not turn Elidibus into Zodiark.