Comment 2 for bug 567361

I don't understand why you think this report was incomplete. Quoting the original above:

             "Currently, gdm --help helpfully advises to use gdm --version
              to get the version number ... "

So, I think the answer is yes, running gdm --version is recommended without restriction by gdm's own inline documentation. Nowadays some form of command-line argument such as --version, -version, -V etc is generally supported in almost every gnome or GNU utility for that matter. Either gdm's documentation is wrong or there is a bug. I'm thinking it looks more like a bug, probably a simple one to fix -- I'd send the patch if I could get linux+X working on this pc.