I don't know where the list came from.
It's not specific to G8 , as you can see there's codes there for items that are not fitted to G8's at the factory (eg: superchargers and turbochargers).
There was a Chassis code come up on a G8 that wasn't in any of the GM Service Manuals, but I found the code on the above list as a Rear Wheel Sensor. So the list above is of some use.
I have no time or interest in discussing errors or omissions in the list......its for info only.