"Could you tell us if it's a crime (or even why it's 'suspicious') to be driving a car in Hackney registered in Yorkshire whether it was a mistype or not?"
yes it would be classed as suspicious, blacked out windows add to the suspicion, have a read up on "county lines drug trafficking", (county lines drug trafficking is the practice of trafficking drugs into rural areas and smaller towns, away from major cities) as Mottie said the Met currently have an anti-knife/anti gang initiative and this will require additional stop and searches for the most minor of suspicious circumstances.
Also is it a problem being pulled over for a stop and search? it delays your point of destination by 15 minutes, if you got nothing to hide it doesn't matter, think positively about the police and its a bit of a non issue. At the end of the day they are doing a hard job trying as much as possible to keep the general public as safe as possible with as little interference as possible.
the MSM really need to stop making such a song and dance just because some black people get pulled over, in a heavily BAME populated city its going to happen. No other skin type plays the persecution card as much as blacks (how many Indians do you see rioting and demanding change, and demanding statues are torn down or complaining they got pulled over for a stop and search?)