I think this is the interesting question. I'm an extremely deep sleeper and almost nothing wakes me up while I'm sleeping, but I've found that I naturally sleep significantly longer if my bedroom has too much light or there's a significant amount of noise around me while I'm asleep. So despite not actually waking up consciously, I think I sometimes end up in this partial wake state where I'm not getting proper REM sleep and as a result, not actually getting the rest I need.

It wouldn't surprise me if this is often the case for people who feel they need more sleep. Having proper blackout shades and full silence (via ear plugs or otherwise) during sleep allows me to sleep a significantly shorter period of time as measured by however long I end up staying asleep. I typically don't use an alarm, so it's fascinating to be able to notice that natural difference in how long my body seems to need before booting back up.

Interesting anecdote - the pandemic is what triggered my awareness of this effect. When I'm at home alone sleeping (typically into the late morning, I'm a night owl), my dog will sleep with me. When my girlfriend started working from home from early in the morning, he would wake up with her and bark loudly at the occasional activity outside. I suddenly couldn't wake up on my normal schedule, even though I wasn't actually consciously woken up by the barking. The thought occurred to me that it could still be the barking and something related to the depth of the sleep, so I tried ear plugs + having my girlfriend close the bedroom door. Suddenly I was back to sleeping normal hours. Years of strange sleeping pattern problems were explained in an instant.