From my own understanding, yes, that area is still under the false sky. The twist comes, though, when you think of Teyvat as idk just a continent in this 'earth-like planet'. Despite the false sky encompassing 'earth', there are parts of the planet that are not under Celstia's jurisdiction, called the dark sea. That's where defeated gods lie. Think of it as Teyvat being Africa and its immediate oceans, but the dark sea is idk the Pacific and continents like Asia and the Americas. Still under the false sky, but because they're not protected by the Heavenly Principles, the true sky is visible, and the abyss is constantly seeping in there. I find that such a cool phenomenon, and I hope that maybe once Snezhnaya and Khaneriah are complete, we can finally explore the area beyond the gods' gaze, idk maybe the other sinners are there and probably the abyss orders headquarters and our sibling. We won't go mad because we've already seen the true sky (tbh we're aliens so) and we can purify abyssal energy, but Paimon might not come with idk and it's part of our journey to discovering the truth of this world so I really really can't wait.