Actually, it is not. When you install an isolated ground conductor and utilize an IG receptacle, the ground prong does not connect to the metalic strap of the receptacle. So, when using an IG receptacle, you need 2 grounds: an insulated green equipment grounding conductor to connect the raceway / outlet box / metalic strap of the receptacle, and a separate isolated ground conductor connected only to the receptacle's ground connector (and run back to the main as NJWirenut said).
The idea is to separate the receptacle's ground connection from the 'dirty' equipment ground.
Hope that helps some.
There are 10 types of people. Those who know binary, and those who don't.