On my iPhone 7 Plus, I have one additional folder selected to sync photos to my phone aside from the main "Camera Roll". I spent the time to set names to the photos I have in the "People" folder. After a sync with iTunes, I noticed that all photos that are in the other folder I am syncing lose the name association. The photos in "Camera Roll" all have retained the name associations. It is making me not want to do anymore syncs to iTunes until I can figure out if it is worth the time to set names back to all the photos from the additional folder.