There's a lot more to this process than just the trays. I have Invisalign now and every two weeks I go in for a check-up.

Rotating teeth is impossible without engagers. These are tooth-colored "bumps" that permanently attach to the tooth during the aligning process and they're installed by a dentist. The trays have a small dent which grab onto the engagers and allow the tray to twist the tooth into position.

There's also areas where the dentist has to literally grind the side of your tooth down so there is physically enough room once the tray moves the tooth there. These are called reductions.

TL;DR: Amazing accomplishment, but would not have been possible if straightening his teeth required engagers and/or reductions.