Sounds like a buffoon, I wouldn't trust a tester that doesn't know plate rules!
It is borderline if messing around with spacing of letters and numbers to make some tortuous name on a vanity plate is legal, although apparently ANPR cameras can still make sense of them, people do take liberties with number plates using strange fonts and such and it does peeve a few fellow road users. MOT inspectors have to pass exams and I do not put 'knowing number plate rules' at the top of my list when they are inspecting car for safety issues.
There seems to be an automatic 'rear number plate dirtying' feature on a lot of BMW and Audi models (along with their non-functioning direction indicators), which was useful with Gatso speed cameras, but average speed, ANPR and newer technologies rely more on front plates, which is great for bikers like me
The German motor manufacturers think tank is working on a similar device for front number plates but it is proving hard to do.