Being aware while asleep is something that can happen to advanced meditators. The more aware you are the more you are there is no difference between being awake or asleep. I haven’t heard it brought up in any other contexts except maybe for lucid dream practitioners. I’ve also read accounts from those who have done dark room retreats where perception of being awake and asleep blur and the perception of what you are experiencing has a lot of mind generated in experiences that can seem very real, dream-like, or using Buddhist language, empty.