I don't understand much about kitesurfing, but my best quess is that the point is not so much going to and fro very fast (as in the last picture), but to do tricks. We observed a big bunch of wind- and kite-surfers yesterday on the Flag beach. It took me a while to figure out that one of them was doing something other than just turning and heading back into the deep almost every approach - a guy with lot of bright orange in both his kite and underside of the board.
I thought his flights (you can't call them jumps any more) with just one hand on the kite handle and board held vertical very cool. He is quite likely well known among kitesurfers - if I ever find out, as I did with Claudine, I will tell.
Watch him also i this little video, coming from the right and flying. I was following the other guy with sweet spot of lensbaby, but he stole the stage, didn't he?
A note to myself - next time, come closer and take a lower position, so the height of the flight was plainly visible