It is the new extension that RAGE uses for sync, hence why it is listed as a bug fix. NVIDIA have supported this since driver version 280.18 (which is why RAGE runs a lot better on NVIDIA).
It is called WGL_EXT_swap_control_tear. Basically it will vsync if your FPS >= 60, and start tearing if FPS < 60. This is the same behaviour games have been using on consoles for years but had never been exposed on PC before (despite the hardware being there).
Rumor has it you set wglSwapIntervalEXT to a negative number like -1 to activate it.
It would have been better if RAGE fell back to 'normal' vsync if this extension is not listed, but for some reason it doesn't (and you get horrible tearing). You can set r_swapInterval in the config file for RAGE to get around this.
JeGX, perhaps you can test it out in your demos?