If he's on his own bike then the number plate will give them all the info they need. He can be caught up with at a later date.
There has been a crack down since i left the UK, back in the 90's it was rare to see a motorbike with anything even resembling a full sized plate.
I've still come across jackets strategically draped over the number plate, number plates moved to positions that are difficult to read, or no number plate at all.
The other thing is IF you think it's likely your going to do a runner why on earth would you have the bike registered under your name anyways.
I agree your theory works for 99% of us responsible bikers, but the number plate is no deterrent to someone that's willing to try and escape from the police.
There used to be a club in the East mids made up of ex-racers, they felt racing had gotten too expensive, so they used their race bikes to bait the police into a chase, that was their hobby.
So it's not THAT hard to get-away from the police on a modern or even older sportsbike if your cool, calm and able to ride well, throw in the congestion in London and you've made things a LOT easier
Not that i'm condoning that of course, the guy was a jerk riding at that speed in that area, never mind the wheelie, so anyone trying to evade to police is a even bigger jerk, my point is that it does happen and it's really difficult on something like the bike shown.