Raymond, as Ned explains above, there seem to be no really good options for the upcoming releases on Mac.  The *ed paragraph below has my best guess at to whether a Mac-IDLE user should install or ignore.
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Basic options A, to hold up the release (indefinitely) on all platforms, has precedents, but usually because of bug(s) affecting more than one platform, and usually AFAIK for at most a week.  We have already closed 3.6 to routine maintenance and merged multiple patches into the future 3.7.3.  Withholding the current set of bug fixes does no one any good except possibly for people using resizable tkinter windows on Mac.

Option B, to hold up the release on only one platform is unprecedented as far as I know.  Option C, to release with one more known bug than we would like is relatively normal.  Given the indefiniteness of a fix, I agree with C.

AS for which version of C, I agree that option 2 above seems least bad.  The main issue with option 1, staying with 8.6.8, is how it performs (or rather, fails to perform)  on the new macOS Mohave.  Before opening this issue, I did fairly extensive testing of IDLE 3.7.2rc1 on Mohave and this was the only problem I encountered.

* As far as IDLE goes, what's new in 3.7.2/3.6.8 are mostly doc changes that are already online.  A user who has not upgraded to Mohave could consider staying with the existing releases. I suspect that a user running Mohave will be happier with the new releases with the tcl/tk upgrade. 

I thought of augmenting the the interactive splash notice, but this would give too much attention and emphasis to only 1 of many known but unfixed bugs, and 1 that only affects resizable tkinter windows on Mac.

Perhaps the hopefully temporary Mac installers should be labeled internally and on the splash screen as ...rc2 even if temporarily included on the 'final' download page with the final releases for other platforms.  I believe some people would object is two slightly different releases were called '3.6.8' and '3.7.2'.