He is lucky it didn't break his back, the way the seat was mounted.
If you have a single layer seat, be it carbon OR aluminum and just have a spacer with a bolt through it, to space the seat off the hoop, you are taking your life in your hands. The seat will "fold" around that spacer and then you have a spear pointed at your back. You either need a big flat piece of plate to distribute the force to a larger area, or build a tubing frame to contain the seat. The latter is how I support the back of all carbon seats
My KOS Demon has a seat back support that is also just a spear aimed right at your spine. I have looked at that and felt the same way. Putting in a plate on that support to spread the impact force is one of the things I plan to do to the car.
