Speaking as a fan of Yoshitaka Amano (who was the artist who did the artwork) you can't really take much out of his art at face value as his art is purely symbolic or metaphorical - also he tends to embelish artwork with his own unique flourishes, and that is pretty much the case with the EW cover of Hydaelyn and Zodiark. Also Amano seemed to have portrayed Zodiark as looking more like Chaos from FFI,
rather than the weird tentacled thing wearing a toilet seat lid for a mask with bits missing from him as he ended up as.
And remember, as we found out Zodiark wasn't even a conscious entity anymore but just an empty shell - really all we did in the Dark Inside was fight Fannyboy wearing him as a suit - so that artwork clearly doesn't give that vibe off either.
It's best to just take what Yoshi said as a red herring designed to throw players off the scent so that they will completely unexpect plot twists (which, after all, makes the story better anyway, or at least theoretically).