The idea of animals (and even objects, like kimono or mirrors) becoming kami (gods) after living (or existing) for a long time (generally 99 years) is pretty deeply ingrained in Japanese culture, to the point where they likely felt the Auspices did not need any further explanation. Live a long time equals become a god - obviously, right? Kitsune (fox spirits) are the most well-known of this phenomenon, with the fox gaining additional tails as it grows older, until eventually becoming a nine-tailed fox, the most powerful of all Kitsune.
Yeah, okay, but that doesn't at all explain how that happens in Othard in the world of XIV, because all of that lays completely outside of the established lore.

I mean Suzaku can literally counteract the Lifestream to resurrect and make people immortal. Not to mention they have the Primal-like ability to remodel their environment, I don't think I've seen anyone other than Primals do that