When villagers see a POI outside the world border, they will try to pathfind towards it (regardless of whether they could get to it) and interact with it if possible, allowing villagers to sleep outside the world border. When a villager rings a bell outside the world border, the bell will spasm constantly as long as it stays outside the world border. Villagers won't ever see the world border as an obstruction when they notice, pathfind towards, and interact with a POI.