Think of a motorcycle. If you put a longer swingarm on it (like moving the hubs back) the bike will be less likely to wheelie, because you're putting more weight over the front end. That's why hill-climb bikes have a super long swingarm on them..to keep the front end down.
Consequently, if you put a shorter swing arm on (like some quad racers will do on TT-style tracks) that's like moving the hubs forward. You're putting more weight over the rear end without moving anything around on the car.
More weight equals more traction.
Now it is true that the farther the tires are from the polar moment of inertia, the slower the car will rotate. If you were to make the car 6 inches longer and 6 inches wider, it would turn VERY considerably less than it does now.