This post piqued my interest because it’s been my experience that if I set Stretch Reminder to be on with a Start Time of 07:00 and End Time of 00:00, I never receive any movement reminder. If I change End Time to 23:59, then it works.
I think this is a bug, but I haven’t yet taken the time to report it (and I do get the Fix-It Friday reminders). It seems to have a problem with the on/off settings spanning midnight.
I get reminders from my watch-47mm while doing “standard desk things”. Maybe my use of a Dvorak layout doesn’t allow for enough movement of my left wrist. 
I also get movement reminders while driving long distance, so at least it’s working (as long as I have the End Time set in the way the watch seems to like).