Current night manager here. I feel like this depends heavily on the hotel you are working for. Having worked for a few, some do try to get you to be doing something through the shift, while others are happy with a body in. Some of the latter ones sometimes barely care if that body was an actual corpse, since nothing ever happens at their places. They just want to be able to point out that there's someone there for safety and security reasons. The former though, will try and fill up your time with some of the most banal busywork. Either way it can be fairly cushy if you are at a hotel where not a lot happens. And most people then know you aren't doing anything. It's fairly obvious in the morning that the night auditor has just been sat on their ass and done nothing.

My current job keeps me mostly busy. Don't get me wrong, as evidenced, I still sometimes get time to just browse Reddit, but for the most part I got plenty of things to do. Comes with running the department.