As of watchOS 6/iOS 13, I’ve noticed some inconsistencies between stand hours and stand minutes in Health/Activity.
Specifically, there are often hours where, inside Health.app, I can see that I have at least one stand minute, but when I view in Activity or Health Stand Hours, there is no stand hour.
This morning, I think I figured it out.
I got up, as I normally do, at 6:55. This is my life hack to ensure I get a stand hour at 6-7 am. I went about my normal routine, making sure I moved enough before 7am to trigger the stand hour. It did.
At around 7:15, I happened to look at my watch again. I still only had one stand hour. I know I had moved around in the previous 15 minutes, so I went into stand minutes. Yep, there was a stand minute after 7am.
At about 7:35, I glanced at my watch again, and noticed there was a second stand hour.
I live in a place that has a non-integer number of hours offset from UTC (+09:30, +10:30 DST). I believe that stand hours are calculated based on UTC, and then offset for the current timezone, wheras it used to actually use the hour within the timezone.
My workaround is to make sure I have a stand minute within both the first and second half-hours of every hour (which can be helped by having half-hourly chimes enabled on the watch).