Authenticated Users cannot be set (anymore) from e.g. Windows Explorer (right click file->Properties->Security Settings->Add "Authenticated Uses" ...
After closing the dialog and reopening the settings, the entry for "Authenticated Users" is still missing).
It is not even possible to query "Authenticated Users" with wbinfo.
The behaviour of a Samba Server is thus completely different than the Windows Server is is suppposed to replace.
Winbind backend: TDB
Right now Samba does not implement all of the Windows security model right now, it rather relies on the Unix model. Maybe we'll get the full semantics later.