As of macOS Big Sur or Catalina, folders shared via File Sharing have a banner when viewed in Finder:
Is there any way to hide this banner without removing the folder from File Sharing?
This banner under Finder's toolbar appears when you explicitly share from "File Sharing" the enclosing folder or volume of the current folder. Remember that Mac admins can always access all Mac volumes even if they aren't listed in File sharing, and try to disable file sharing other than users' home.