When iOS 10 came out, I spent hours going through my photos on my iPhone merging and tagging faces. I was really disappointed when I realized none of that effort sync'd across devices. Today, after updating to iOS 10.1, my phone is rescanning all 24,534 pictures again. It appears to have saved the tags, because the faces it's found so far are being given the correct name, but why is it scanning everything again? My iPad (old Mini-2) isn't scanning everything again after updating it to 10.1.