I'm glad you got it working.  The information at https://www.python.org/download/mac/tcltk/ pertains primarily to using Pythons from the python.org installers; it doesn't directly apply to Python instances built by and supplied by third-party distributors like Homebrew or MacPorts.  So there is nothing wrong about them supplying and linking their Pythons with their own version of Tcl/Tk, be it 8.6.x or 8.5.x.  It would be good to figure out what the problem was that you saw and whether it is a general problem for other Homebrew users but that is out of scope for this tracker.