Explain to me
How I can get up at 6am and hit 12hrs of standing before 4pm? How I can go for a 20 min 1mile walk at 1pm and still be at 11 min activity?
Are you wearing your watch when asleep? If yes, then you are
active enough when you are sleeping that the watch thinks you
have stood up. I get this occasionally when I toss and turn.
While walking, the pace must be brisk enough to raise your heart rate
for the watch to count the movement.
Perhaps the article in this link will explain it better than above:
https://www.imore.com/apple-watch-activity-tracking-5-tips-you-need-know