If you did get stopped by police and claimed you had DOC on your policy would they actually follow it up? A mate of mine who's 20 drives his dad's E46 M3 via DOC and I dread to think what trouble he could be in if the police stopped him.
If he's got DOC he wouldn't get in any trouble as long as there are no clauses that state he cannot drive such a powerful car.
Chances are if you got stopped on a test drive they would check the car had insurance, realise it was insured but not too the driver and then ask you to prove you were insured. When you claimed you had DOC they would usually phone up the insurance company or a number the police have a check.
At least thats what they do on Road Wars.