Vantage is'nt a CPU benchmark. It's a Mix of both, more on the lines of GPU... Now, Mark06 will be the CPU hungry benchmark. To where Physx doesn't even work unless you have one of the cards.
Now, for the reasoning on Physx.. Their not fake, its just that instead of relying on the CPU do do it's OWN physx, the G92 and above chips on Nvidia have the ability for physx. Then the GTX 2xx series cards have their own Cuda built right into the card it self..
There is nothing faking about it. Just the fact that Newer Nvidia cards have the ability to take away the CPU's job of Physx.. Less strain on the chip..