Insurance : Named driver on two cars

Hey, just wondering if anyone could clear this up for me! I'm a named driver on 2 cars owned by my Dad. I'm a 20 yr old male, so obviously I hike up the price on both cars.

But here's the thing, my uncle (who is with a different insurance company) bought a second car the other day. Both him and his son (19) were insured on the first car, but since the new car has a much bigger engine, he expected the cost of adding his son to the insurance of this car to be huge. But the insurer told him that the "loading" associated with the young male had been charged on the first car and he was able to insure his son at no extra cost!

Is this standard practice, or should I change my insurance over asap?