It is only a reference to the universe, to the existence that surrounds them, not to other worlds, if it were the multiverse, Okada would have simply mentioned all the universes or the multiverse, being one of the few authors that actually uses this word, but he never mentions that in that scene. You can even see how everything that happened in that world does not interfere with other worlds and only affects this one exclusively. The only mention of these gods interfering with other worlds is the fact that they sent Ikki, Shiryu and the other Saints to other worlds to eliminate them from this world and invade it without their intervention.