It may not make sense, but I've seen it supported in the wild, in a different library.  Of course, we *did* treat it as a bug in our code and fix it once we realized that's what the library was doing (we were inadvertently passing it None for the hostname, and its response to that was to not check it).  So I think Antoine is probably right here.  Especially since this has never been reported as a bug by someone trying to use it in an application.

Since it wasn't documented, perhaps we should just add a deprecation warning (that says it is a noop) instead.