WWII may have been an exception, but I don't think you got drafted in the Merchant Marine, but it did count as military service.
I always tried to work the afternoon shift because it was important to me to sleep in mornings.
Probably true but I also posted above that it could also have been a matter of him about to be drafted so he joined the Merchant Marine. And soon after shipping out the War ended so he returned to his beloved long afternoon naps.