Product review (4 stars): Ground Wire Not Threaded--Had to Drill it Out
Ground wire wasn't threaded for the screw.  Luckily it was soft enough that I could take a screw from the old unit to create the  necessary threads.  Unfortunately it wasn't perfect and stripped a bit, but it's working.

The old unit looks like it was manufactured pre-threaded, so I'm not sure why the unit I ordered here wasn't.