That’s an excellent point. However, I don’t know if it’s technically possible since the video has to be recorded and sent to the cloud before being analyzed for PD. I suppose that after the video is analyzed, it could be auto-deleted and the cooldown period reset if no person was detected. That might be feasible, I don’t know.
I will move this post this topic over to the wishlist with a title change to reflect that possibility. (Be sure to click the VOTE button at the top.)
All that said, I think the solution is going to be using Complete Motion Capture in conjunction with PD. Unfortunately, that does require a subscription. Also note that for the time being, PD & CMC do not work together (yet). They are planned to work together, however, by the time PD is fully released.