I also often wake up before the alarm, and the delta is on the order of tens of seconds. I'd say I definitely get to become fully awake and start thinking about the upcoming day before it rings. Apparently, just a matter of quite a precise internal clock.
Another situation when it can trigger is when I brew tea. I like a "reproducible" brew, so I'm used to setting the timer to 3:30 minutes after filling the cup with water. When I then go do something else and become engrossed in it, I'll often suddenly realize "Oh no, what about the tea?" I then look at the timer and see there are 5-10 s left.
Another situation when it can trigger is when I brew tea. I like a "reproducible" brew, so I'm used to setting the timer to 3:30 minutes after filling the cup with water. When I then go do something else and become engrossed in it, I'll often suddenly realize "Oh no, what about the tea?" I then look at the timer and see there are 5-10 s left.