A few comments on this.  One, the Tkinter documentation in question seems to have been a personal project of John Shipman at New Mexico Tech and, as such, was not "official" so I've updated the issue title accordingly.  Sadly, as Cheryl noted, John died two years ago and I guess there were no plans in place for someone to take the documentation over from him.  We can all appreciate his very valuable contributions over the years by developing and maintaining this additional documentation.  It would be great to find a way to provide an equivalent resource for Tk 8.6.  The best alternatives today is probably Mark Roseman's TkDocs website and "Modern Tkinter" book/ebook, both also already linked on our Standard Library tkinter page. I've nosied Mark in case he has any thoughts on the matter.

As far as updating the page in older releases, as 3.6 release manager I did decide to allow the update there, even though we normally would not make such a change for a security-fix-only release; I did so as we are still including 3.6 in our daily doc builds on docs.python.org (although at some point soon that will stop).  It's Larry's call about 3.5 but note that the current 3.5 docs on docs.python.org are normally only updated when a new 3.5.x security-fix release appears. If you want it to be considered for 3.5, it would be best to make a 3.5 backport PR.