why can't i identify people when editing a photo in a shared album apple photos

I have lots of photos in my library. All seem to be able to use the face technology so I can find great shots of family and friends later on. However, When I add photos to a shared album it appear that the face detection technology and even the manual faces I have identified seem to go away. T top it off the shared photo no longer resides in my library so the work of manual identifying people seems to be lost. Help? what am I missing? Do I need to simply get rid of all of my shared albums to get a complete picture/inventory of all of my photos.