As explained to me by a sleep doctor, sometimes people do feel as if they didn't sleep after a nap, but still feel rested. We often don't remember stage 1 or 2

As explained to me by a sleep doctor, sometimes people do feel as if they didn't sleep after a nap, but still feel rested. We often don't remember stage 1 or 2 sleep but that doesn't mean we didn't sleep. So yes, a nap is valuable even if you feel you didn't drift off, but it is not necessary to invoke mental energy expenditure as an explanation.