Intel appears to be offloading some of the work associated with the GPU tests onto the CPU in order to improve 3DMark scores. When asked for comment, Intel replied with the following:
"We have engineered intelligence into our 4 series graphics driver such that when a workload saturates graphics engine with pixel and vertex processing, the CPU can assist with DX10 geometry processing to enhance overall performance. 3DMarkVantage is one of those workloads, as are Call of Juarez, Crysis, Lost Planet: Extreme Conditions, and Company of Heroes. We have used similar techniques with DX9 in previous products and drivers. The benefit to users is optimized performance based on best use of the hardware available in the system. Our driver is currently in the certification process with Futuremark and we fully expect it will pass their certification as did our previous DX9 drivers."
This CPU-assisted vertex processing doesn't appear to affect Vantage's image quality. However, Intel is definitely detecting 3DMark Vantage and changing the behavior of its drivers in order to improve performance, which would appear to be a direct contravention of Futuremark's guidelines.