When I was kid I use to get on one of these quite a bit.
One day I was on it and one of the cords snapped when I was way above those poles and I went straight for one of the poles on the way down. I was lucky enough to put my arm out so I didn't smack my head. My arm hurt like a motherfucker for a week, I can't believe I didn't break it.
Now imagine if one of those cords broke on what that girl did in the video, you would probably go straight for a pole if it snapped right when they let go... Needless to say you would be dead as a fucking door nail.