After more research, I am more inclined to add the keywords to the global identifiers list. The IDLE doc says that they should be present.

"Show Completions
 Open a scrollable list allowing selection of keywords and attributes."

If this issue were rejected, the line above would have to be changed.  (Other needed updates are another issue.)  It was added to idlelib/help.txt (since replaced by help.html) by KBK in

Revision: 209de1f6ca1beaaa6b5eeb413f02e9c8c334ee50
Author: Kurt B. Kaiser <kbk@shore.net>
Date: 2/8/2007 5:58:18 PM
Message: ... Added AutoComplete instructions to IDLE Help.

(I checked 2.6 fetch_completions and keywords were not actually included in the global ('') list.)

The completion menu entry was copied to idle.rst in patches for #5066 by Jessica McKeller and Todd Rovito.  Both docs were updated.  Another 5 people, at least, reviewed, including 3 core developers.  It was committed by a 4th, Andrew Svetlov.  So 9 people besides me did not notice the discrepancy and may have thought 'keywords, fine', like I have been.

One can invoke Show Completions not following anything to get a list of names that one should not use.  For that use, keywords should be included.  This list currently has 230+ identifiers, 150+ all lowercase.  keyword.kwlist would add 32 (35 - 3 builtins).  It is not a huge increase.