The human may in fact be guilty.
I do not recall the steps I took when I installed mingw, just that I did, and now that I review the mingw install instructions, it says the person doing the installing needs to add the mingw references to PATH. It's possible I accidentally added them to ComSpec, though they were also present in my path as well as the comspec variable. Possibly, I recognized my error and then failed to remove the erroneous entries.
So I wouldn't be so brash as to point a finger at the mingw installer. It may very well have been me.
It's interesting to note, however, that as soon as I posted my successful resolution to the problem on the Google bug report site (I did file a Google bug before coming here), someone else replied encountering the same problem, nearly identical except that his ComSpec value had python references added to it instead of mingw.
So, I may be guilty, but at least I'm not alone.
Jerry