It's a bit of a silly rule IMO. It allows cars to have a black-and-white plate when it wouldn't have been fitted in period. Bonkers.
I fully agree.
It just looks wrong when you see a B&W 'P' plate on a 1976 car, as it has never been legal until now.
It looks just as wrong as those horrible "age-related" plates that the DVLA like issuing, which look to us anoraks exactly like replacement plates for ones which have been nicked and sold on at an astronomical price, thereby totally ruining the originality of the car they came off...
It seems most car nuts aren't bothered about plates. I frequently see veteran cars with modern reflective plates.. Who would do such a thing?