It depends on how the system is proportioned. Not all methods are linear; in fact most aren't, and have at least a knee point and then become linear after that. I don't recall if it was on the contours from the beginning or not, but the later cars have EBD, which uses the wheel speed sensors to decide when to limit line pressure. Also some OEM prop valves are sensitive to weight transfer, like the prop valve in my XR4Ti; and limit pressure as the vehicle pitches forward (a sign of weight transfer).
I guess one of the main points that you are missing is that in a car like the contour, you don't WANT the rear brakes to be doing more, unless you have drastically changed the balance of the vehicle or the brake system proportioning.
A good case in point is the Mustangs our team races. We run larger wilwood brakes up front, because that is what is allowed, but the rears are still stock parts, because the stock parts will provide all the brake torque we can use, even with the race tires, and the modifications we have made to move weight to the back of the car.
