This is dumb. They aren't even backflips (they're back handsprings, and he doesn't even rebound properly while doing them), and they're not that hard. They're more about having the courage to launch backward than athleticism. I routinely teach my most non-athletic friends how to do back tucks, which surprises them since they think the trick is difficult to do.
For what it's worth, I just did a one-legged back tuck at the gym today despite a torn ACL. It's not that hard if you know the technique and are unafraid.
I firmly believe that football players should learn gymnastics, as the flexibility, power, fluidity, and balance are all applicable to the football field. In fact, I want to open a training center to teach athletes more effective means of moving.
Just doing back handsprings, or jumping out of a pool, however, simply proves you can do a neat trick.