But are we actually to be considered 9/14 aether-wise?

[Cleretic]

Not that it disproves your argument, but do remember that those Ancients were also sundered together with Zodiark. So there's moreso a bigger pool of souls to pick from than other souls being rejoined.

I still get the idea that the souls in Zodiark were actually fully intact, and just separated. Real Hythlodaeus seemed the same all three times we met him, after all. Those full Ancient souls--whether or not there's two or two billion--are basically a problem for outside of the game's scope, since it'll take by my estimation a good eighty years for them to get recycled (using Gaia as a sample-size-of-one example).

As for us, I've seen no evidence that us having more of a rejoined soul matters at all. If more soul equaled more better then Shadowbringers would've been an entire expansion of the experience of farming for monster mats in a low-level zone. Yeah, our soul is bigger, but it's not giving us a lot of benefit.