Same thing was happening with my series 7 after the update to 10.1 - battery drain from 100% to 10% in a matter of hours. Tried the hard reset mentioned but that didn’t fix the problem. I also have the Moby watch face app but hadn’t seen the suggestion to uninstall it. What I did do was unpair the watch from the iPhone 14 Pro Max and pair it again. Problem fixed and I haven’t deleted any apps including Moby.

After the 10.01 update my series 7 battery would go from full charge to lass than 10% within 3 hours. I tried the hard restart, put my watch back on the charger and the same thing would happen. Finally I unpaired the watch and paired it back and the problem has been fixed.