In my kiting (including kitesurfing) experience, I've been trough a lot of crashes, and the only reason I am here to tell the tale, is that always I had a safety release at hand.
Manny moons ago, the foils were the only traction kites (we did not had inflatables), safety leashes were not so effective on a briddled foil, so we were experiencing lots of models and solutions (all home made), but in almost all the cases, a safey release (to ditch the beast) on the leash was paramount in saving our heads and limbs!!!!
A piece of rope is a "suicide leash"

Why people keep using them, thinking that it will not happen to them?
I hope that at least they will have a pretty sharp knife with them (if they will have the time to cut the leash).
The best type of leash is the one that disable the kite! I know, you end up with the lines "spagetti".
I use one of those, and it is effective even in high winds - if I feel I will end up being "tea bagged", i just pull the pin and the kite is flagged. A littel swim back to the beach, half and hour to untangle the "spagetti" and that's all.
As I always say, safety is a matter of choise!
You can lead the horse to the water, but you cannot make it drink.