This rider was incredibly lucky to have suffered fairly minor injury in a flat kite accident which could have EASILY been fatal. Other kiters on the beach might have also been seriously injured as well. He couldn't see the kite being launched and the helper may not have been all that familiar with flat kites. Some things to think about related to assisted launching and past accidents appear
HERE
Both are very experienced with C kites. Hanging on to a kite for launch in high wind and blasting sand isn't all that easy a proposition particularly when the kite is near its upper wind limit. The time to experiment with new gear is not in such extreme conditions. Also, avoid "soft" leash attachment clips, for a good reason why click
HERE
Another kiter had advised the rider not to attach his leash to the chicken loop but instead attach it to his Oh Shit handle and shift it over once well offshore. The rider was not that comfortable with this as he was used to suicide leash attachments on C kites through the chicken loop. NOTE: There are significant DIFFERENCES between flat kites and C kites, learn what they are by carefully reading the user manual, talking to other kiters and carefully building experience with the flat kite under controlled circumstances. Just because you are used to attaching your leash to the chickenloop or even the bypass leash attachment, doesn't necessarily mean this is a good place to attach to while near shore. In the current case, attaching to the Oh Shit handle until well offshore and then moving it to the chicken loop would have made more sense. What happens if a bridle breaks? Maybe something not all that different.
Make sure you know where your leash attachment quick release is and be familiar with activating it. On top of your butt may not be the best location for this either. Too many kiters ignore this simple step in self preservation along with even practicing totally depowering their kite. "I'll figure it out in the emergency," unlikely.
A stopper ball can simulate some of what happened in this accident. Don't engage stopper balls on flat kites nearshore or when you might potentially crash (i.e. before jumping).
Experienced guys don't need helmets or impact vests because ... ? Luck is great while it lasts but some basic safety gear may stretch your luck when you unexpectedly get dragged south at lightspeed someday. Overconfidence can be a killer not only in kiting but in many action sports. Flat kites may reduce kiting fatalities but the capacity to injure and kill is still there. Be careful out there.