Nick you are 100% correct, after reading you post I grabbed one out of my truck, and yes the plate screw is connected to the yoke, so I will shut up about the metal plates.
As wrong as I was about the plate issue I still say it is easy for the IG to compromised in even with the most careful installation, by the end user.
If the prints call for IG I try my hardest to make that happen and it is a pet peeve when I see the building occupied and the IG end up jumped to equipment ground.