A managed account is a MDE account created under another account. Like a child's account which was created in the parents.
We did not have a dummy account, because we split it between 3 families last trip. My mom bought the MM and linked it to her account. In her account the people with their own regular MDE accounts (me, my brother, his wife) show as "can view and purchase your PhotoPass photos." Those that are a managed account (my son, my nephews) show as "cannot view your plans or photos. More Information", but photos scanned to their bands did show up in my mom's photopass account. I don't see anyway to change the setting for a dummy account. My assumption is that as long as the person who manages them can view photos, then the managed account is able to use their band to add photos.
My mom made a "managed account" for everyone when she made her Disney plans. This was a huge pain in the butt because we had to call Disney and get the real people switched out with the ones she created so that we could make FPP in advance. On the trip she called in a panic (after I had left) because she couldn't make fpp for NephewL. I made them through the app for the group and that was that. Until I went to download our MM pics. I realized there were quite a few missing. That's when I realized she had never connected to my nephew's real account (the managed MDE version which his tickets and room stay were linked to). I sent the invite to my brother from her account, he accepted and then voila, the missing pics showed up. It must have been my nephew's band which was scanned for those.