Does using a standing desk "count" when using the Apple Watch to close rings?
Since WATCH is worn on the wrist, if your wrist rests the same way while you’re standing as it does while you’re sitting, then that time is not going to count as “standing.”

Normally it is best to walk around with your arms swinging freely for WATCH to detect that you stood. That is why the Stand reminder tells you to move around. The current research also suggests that you need to move around to counteract the negative effects of sitting for too long.

My experience has been that at a minimum, you need to hold your arms down your sides for WATCH to detect that you are standing. That is not 100% reliable however, and it is best to take a quick walk (especially since you can no longer use your hand to type anyway).

Either way, if you keep your hands on your keyboard the entire time at your standing desk, WATCH will not detect that. Another good example is cooking/doing the dishes. You will get Stand reminders while performing those activities, which typically require standing.