This behavior is a ns6 legacy. Its reason was: administrator (that is not root) must always be entitled to modify (fix) any shared folder.
In ns7 we are discussing a feature that could overcome this limitation based on “username map”: please chime in! Of course “inhert owner” could be set “no” if we find another way of always granting access to admins.
Meanwhile your boss could appreciate the samba-audit module that tracks all operations executed on shared folders.