You are right. To be exact, it's the same as "chmod a=,-s,+rwX FILES" (to handle directories SGID and SUID also). Then, these patchs are not usefull, but yes, a few lines more - with this example - in documentation would help some guys like me.
Isn't the proposed "chmod --umask FILES" almost the
same as "chmod a=,+rwX FILES"? If so, perhaps all we need
to do is to update the documentation to mention this
already-standardized solution to a common problem.