I noticed that the first day of the week in the Samsung Health app on the Galaxy Watch 3 is persistently showing Sunday instead of Monday when checking the workout information for the week. Ironically, the Calendar app on the very device is showing Monday as the first day of the week, same as it does in the Calendar app on my Note 20 Ultra. I know, first world problems. But c'mon, this is just poor programming at this point and these devices aren't particularly cheap. Would be great if someone knows a fix for this silly issue.
I agree this is poor programming. If you are really annoyed like me change your system input from English (US) to English (UK). Then, you will see everything on watch and Samsung Health starts from Monday.