Of course. But the point is that an RC car is in a different category. An RC probably should fail a VIN check digit routine. Now, if that check is always off by the same amount for RC cars (i.e. constructing the check digit adds a constant for all RC cars), that essentially gives a second check. So a check digit routine can pass a production car, or fail but notice that it is a pass for an RC car, or fail for both. The RC check will have a slightly higher false positive rate, but who cares for a few hundred cars at most.
Thank you kindly.