As a teenager I built rockets just like his, a stick of balsa attached to an Estes motor. I launched them out of a lacross stick. They flew a lot straighter than his rockets, so I am guessing that a longer launch tube would make the difference on his bike.
He's taped the balsa on, and I glued mine. Possibly his rockets are leaving the balsa fin behind.
Either way, extremely cool, and I hope he doesn't get caught!
Frederic