I expect as the caffeine takes a while to metabolize. They'll get the rest naturally from their body, and about 30 minutes later when they're ready to wake up - the caffeine will also be kicking in to give a nice jump start.

Here is an interesting guide from the Royal College of Physicians (UK) that recommends a caffeine nap to help with the night shift.

The sections on Napping, and also the section on Caffeine are interesting. The gist of it is the caffeine will take 20 minutes or so to take effect, so by combining it with a short nap you get a double whammy.

https://www.dgeducationcentre.co.uk/wp-content/uploads/2016/...

The caffeine takes about half an hour to kick in. When I was in college I would drink a cup of coffee then take a half hour nap. I woke up feeling great and ready to work.

A coffee nap has a stronger effect than coffee or nap alone.

For me a nap is enough, usually set the timer to 12 minutes but feel energized after 10.

Caffeine withdrawal takes two weeks but was worth it. My ADD gets worse on it. Combined with Methylphenidat it feels like trying to drive full throttle into a dead end with a drawn handbrake.

A study I read yonks ago concluded that consuming caffeine and then taking a short nap made it very effective at increasing productivity.