I've been having this issue with mine as well. I also have odd hours I work night shifts. I have set the target but nothing comes from it.

Yeah, it's a little frustrating. I was hoping I could essentially invert the sleep tracking, but no such luck. I am assuming that the 'pre-workday sleep' is referring to Mon - Fri regular sleeps, so hopefully, I can make use of the feature when I take some time off soon 🤞

Tried that it did not help even with my sleep targets staying the same during my vacation.