Here is a video of him in the long jump:
https://www.youtube.com/watch?v=HNtZ_lbhafE
It does look a little strange, but not crazy. His turnover on the runway is a little higher than most jumpers would have. He does appear to get a bit more lift than most jumpers do.
Most elite LJers probably could get that much "lift" off the ground, but only by getting the heel out and really losing speed, he seems to be able to get that lift without trading off horizontal speed nearly as much as an able bodied LJer would have to.
I'd say he has a clear advantage over able bodied jumpers. I would be interested to see what his horizontal speed is at the board. I would be it is well slower than the other jumpers, but the advantage he gets from his spring is unfair. It would take a better video to make an estimation of horizontal speed on the runway though.
Imagine how far he could jump if he was an elite athlete with one of these blades to jump off of, rather than an above average athlete with one of these blades to jump off of!