My friend is the admin of a local Facebook Group. Apparently, Groups can allow "anonymous" posting if the admin enables it. I looked up what that meant in Facebook terms.

If you post anonymously, your name and profile picture will still be visible to the group's admins and moderators, as well as to Facebook. Normal users just won't see them.

That's not anonymous.

Nostr fixes this by allowing anyone to be as anonymous as they choose to be.