That kid wasn't a scooterist, he was a twat on a twist and go who will run out of skill before very long riding like that - what a muppet
I pulled up at a set of lights on Friday evening after work on my m/bike next to a guy on a fireblade, and there were a couple of kids on these twist and go's in front of us. Lights change to green and we follow them for about a mile. Sure enough, they just both behaved like a pair of idiot weaving, tailgating, cutting really close to the cars on the roundabouts. You just want to give them a wide berth as you know that if you get anywhere near them, they will try even harder to behave like idiots and squeeze and extra 2mph out of their hair dryers whilst totally ignoring any of the other potential hazards on the roads. If I were their dad, I'd ban the buggers from using them until they had done a bit of training.
I consider a 'Scooterist' to be someone who is riding a classic bike like a Vespa or Lambretta - and these people are absolutely dedicated to their hobby. You could buy a very nice superbike for what a classic Lambretta goes for on the open market.