I think that PP gives you a base guide in basically simple performance stats. PD probably has a program that takes given car values(power and torque, weight and weight balance and downforce and drag coefficient) and simulates sprints, slalom and lateral G then gives you number value for that car as it's rating. This is why I think the majority of cars fit the category of being in the ballpark of performance which is fine, but it's very clinical and doesn't take into account the driver nor the vehicles inherent abilities.
Notice that the NSX for it's power and weight is deceptively fast when stock, especially in a straight line but the key to this car lies in it's relatively easy handling. NSX is incredibly balanced and it's output through it's rear wheels is just spot on, notice the RX7 is the same as well, it's FR but has very neutral handling and is very fast in a straight line. Not everyone can drive these cars and win easily, it still comes down to the one controlling the car.