I cannot take that too serious. It purposely try to paint it as a very dangerous activity. Landing out of phase is not the same as landing on a hard surface, at worst you get propelled up way higher than you're comfortable with, and it's certainly possible for 4 children to launch one of them high enough to clear the safety net.

And you know what, that is okay. Because it's one of the less dangerous things children can do that improve their physical understanding and ability. Certainly beats them trying to get on the roof of the playground.

But I agree that safety nets, or trampolines dug into the ground is a very good idea. Actually, both would be the best.