Thanks for digging up the history.  I would have approved without, but feel better with.  Using the colorizer close method to close a window seemed flakey to me, and it seems someone else thought the same long ago.  I suspect the machinery was left to avoid breaking external uses.  PEP 434 changed this avoidance being *necessary*.  (I am sure I have seen a SO answer with percolator + colorizer, as in turtledemo.)

IDLE has had a too many shutdown bugs and still has some.  Not adding one was my main concern when reviewing.