Who knows with the DVLA, but if stopped and I still was under the year on my US drivers license, I would simply show that to the cop and not mention my provisional. I will admit to pulling the "stupid American" when it works to my advantage.
Needless to say, it didn't work in the Paris Metro when I was out of zone, but then again, my British co-worker insisted I didn't need a carnet for the zone because "no one ever checks". The bastard didn't even have money on him for the on the spot fine that levied on the both of us. I had to pay the whole damn thing and then run around Grand Arche trying to find a cash machine that took me card!