I do those on a slalom ski for my show ski team... alex is right it is all driver, it is the same concept as the turns on the Seisitec 2.0 system all you have to do is stay on edge and keep line tension until the boat makes it out of the turn. the most dangerous part in that video is it looks like they are pulling it from an extended pylon and if the pull was strong enough it could definetly bend the actual pylon. During our ski shows we use Ski Nautique 196's with the extended pylon up to the height of the windshield and the toughest part about pulling them is keeping line tension so the rope makes it around the bow or else there is a possibility of running over the rope (which we have done before)
heres a picture-