Remember that the code is _nothing_. Just some words on paper, the distilled experience of more than 100 years of thousands of people. Even if the code says that something is explicitly _not_ allowed, the code itself has absolutely zero capability of enforcement.
It is only when some government agency 'adopts' the code as law that you get enforcement. There is nothing that says that some local government couldn't adopt an entirely different code, or make up their own code, from scratch.
It is entirely normal for local governments to adopt the NEC with local 'amendments'; for example the requirements for using pipe in the Chicago area for things that everyone else permits the use of NM cable. If the local AHJ says you can't connect the GEC to the meter base, then that is the local code.