I learned something from this, Chris.
Regretfully, it assures me that there are others (like myself) that are very handy and certain that they have hooked things up correctly because everything works and the 3-light plug checker shows "all systems go". Maybe they really aren't...?
For instance, I know that I have a sub-panel out in my garage of my principal residence. I also know that the neutrals and the grounds are all connected to the same buss bar inside the subpanel load center within the garage. This should also be changed to isolate the grounds from the neutrals....right?