As Zero-ELEC said, they give an explanation, but it's very hand-wavy and doesn't make sense. In short, those quest-givers are indeed computer simulations, just like everyone else in Living Memory. I assume they just struggled to find a way to have quest-givers that existed both before and after the MSQ completed, and so they settled on something flimsy that they felt was passable enough. Not the worst plot hole in Living Memory at least.