So after that mess of Surtalogi lore where they decided to make the abyss some kind of universe-scale threat, are they just tossing out the whole cosmology they came up with before of Teyvat being based around 3 realms and the abyss being the void realm?

Presumably the realms are meant to be of relatively equal standing, so it doesn't really make sense for one to be universe-wide and the others just part of the system of Teyvat's world. It feels like half the time they forget that the light realm is supposed to be there as a counterpart to the abyss because they're so big on doing this sci-fi universal conflict angle now.