What John is saying is you don't need IG hardware if you run a dedicated circuit in a plastic box. The ground is "isolated" simply because there are no other connections.
The NEC is simply recognizing that IG is really designed for places that use metal raceways that are also incidentally grounded a number of places in the building, creating ground loops.
IBM decided in the late 80s that IG was snake oil and removed the requirement from the physical planning manual. Unfortunately a lot of people who should know better did not get the word.
