A definition from an online dictionary [of 'driven']: " Powered, operated, or controlled"
At no point is a co-driver operating or controlling the vehicle, except in special circumstances.
Sitting in the passenger seat, you are not operating any form of controlling mechanism to dictate the velocity of the vehicle.
And I don't know about anywhere else, but I certainly would never, ever say that the co-driver is driving the vehicle. The most they can do to dictate the direction of the vehicle is to tell the driver where to go, which is not directly having any effect on the velocity of the vehicle in any way.
I didn't post about the Dodge Viper, Ferrari 360 or Morgan Aero 8, because I wasn't driving them. If you want to post about what cars you have been driven in, fine, but this isn't the right thread to do it in.