Unfortunately, it isn't only the transporter than can add miles. Two months ago I bought a Challenger, supposedly with 11 miles on it which is about right for a new one.
It arrived with 59 miles on the odometer. Turns out the dealership had driven it from one of their locations to another, not had it transported as they said they would.
A few years ago, bought a Challenger with 16 miles on it. When I arrived to pick it up there was 50 not easy miles on it, as evidenced by the rear tires.
Valet mode or not, you win some and you lose some. Both of the above cars were off the lot, though. With ordered vehicles I've had better luck, one with only four miles on it, and I think 12 has been the highest.