I think it's more like "You can banish that one small facet of them". They're still all bound in the prisons the Titans made, and what we end up fighting is basically the finger they pushed through to poke things with.

They're kinda using the Tolkien method of immortality, they've so infused the world with their own power that so long as the world exists, so will they. Even if it appears they've been killed, they'll return eventually.