I created a managed user for my wife, but, on her laptop, she cannot select multiple files and set a rating for all of them at once, in the manner that I can. She can set ratings per tracks individually.
Ok… I see.
I believe what you see is “by design”. They can rate the media you have shared with them – however that’s only available on a per-item basis.
Managed users (or friends with whom you share a library) however cannot edit your shared library. You happened to use the mass-editing of your media to also set the rating for all those items.