Yes, that's probably the other side of that puzzle that I found really interesting, I think he explained it with the example of the fire fighter that would wake up seconds before the alarm would go off, and the experiment with the electrodermal measurements with the randomized pictures, because I've experienced the unexpected out of regular cycle awakenings, specially during stormy nights, right before thunder claps, I wake up to witness it happen awake.I thought that was very appropriate. When I used to make 24-hour shifts in the deep Spanish countryside, normally I would be on call in the health center. In a good shift, you could sleep all night. In high season, you would be lucky if you slept a couple of hours. Regardless of the tiredness, I would usually wake up before the phone rang with an incoming emergency during the night. Like I would sense that someone was deciding to call at that moment for their emergency and as the phone rang, I was already waiting for it. It's really less traumatizing that way.
Because on the one hand, the regular cycles and circadian rhythms of your body, as well as routine, can probably explain waking up before your alarm goes off, maybe even as an adaptive response to stress, in order to avoid the stress of horrible alarms, you'd adapt to wake up before them, provided you have a regular enough schedule. But the unexpected events that you still wake up before, those are interesting.