In the video above (at 41 secs), the guy pushes another cyclist on the ass. The purpose is probably to avoid crossing wheels and benefit from his draft but I find it very strange. I also saw it at some stages of TdF this year. Is it something normal in the pro cycling world? Honestly I don't want someone to touch my ass when I'm going downhill at 100 kph.
Another thing is that I find drafting useless in this case since the guy on the front has reached limit speed. They should have reached a speed where max cadence and top gear ratio wouldn't work anymore. The only advantage of drafting could be less wind on your face.