In IDLE 3.6, open idlelib.macosx (^M easiest).  Open Find in Files dialog (Alt-F3), enter 'isAquaTk' (without quotes), and go.  Output for me currently looks like
...\idlelib\macosx.py: 9:     warnings.warn("runningAsOSXApp() is deprecated, use isAquaTk()",
...\idlelib\macosx.py: 11:     return isAquaTk()
...\idlelib\macosx.py: 23:     isAquaTk(), isCarbonTk(), isCocoaTk()...
...\idlelib\macosx.py: 39: def isAquaTk():
...\idlelib\macosx.py: 226:     isAquaTk(), isCarbonTk(), isCocoaTk()...
...\idlelib\macosx.py: 230:     if isAquaTk():

The first 4 line numbers are correct.  The last two should be 232 and 236 to match the editor.  Or the editor numbers should be 226 and 230 to match grep.  I have not yet tried to cound to see which is correct, or look to see if there are long or continued lines that might throw one count off.  I should copy the file and delete lines between 39 and 226.

FWIW, using an IDLE built from the current top-of-trunk default (on OS X), the steps outlined above produce the correct result, 226 and 236, which match up with what other tools report.

Yesterday, I grepped three times and got the same wrong result each time, so I know I was not crazy.  But today, starting fresh with no IDLE or TortoiseHg running, all is well.  Closing as 'heisenbug' ;-).  Lesson: start fresh before reporting weird behavior.  (I should have known.  I occasionally have to reboot windows to reset its key mappings.)  Thanks, and sorry for the noise.