Years ago, when I did testing, they would put us in vehicles as equipped, and have us go through a bunch of tests, including skidpad. One thing we found out during these tests was that cars do better on certain tires. One car may perform well with low profile tires, and another may not. Or, one car may like Bridgestone tires, for example, and another may not. Therefore, putting the same tires on 2 vehicles may not make them equal in that regard.
Generally, a good driver is a good driver, but not always. In general, I could beat the manufacturer's specs on just about any car they threw at me, but every now and then, I'd miss something on the slalom. Since we only got 2 attempts, I never got adjusted to the car.