This explains a bit better what the issue is: https://en.ilsole24ore.com/art/facebooks-data-protection-reg...
TL;DR: they didn't thoroughly explain the users what they were consenting to when giving the app access to the gallery.
WhatsApp has a similar issue. You can't share just one photo, you have to give it access to all photos.
WhatsApp has a similar issue. You can't share just one photo, you have to give it access to all photos.