I guess the confusion is that how would they change the village based on AI behavior if that AI isn't always simulated on the background. Obviously they don't need to render it graphically when you're not there, but you'd expect the village to change when you leave and come back. Could they just quickly run the simulation or "predict" what changes would have occurred when the chunk is loaded in? I'm genuinely asking, because I don't know how this stuff usually works.