OB, if you were assessing me; a player jumped with leading legs into a player waiting to play the ball; I gave the jumping player a red card for dangerous play, which law would you rely on to criticise that decision? Even if the jumper landed on his neck and left in a wheelchair!
In any other situation on the rugby field there would be no argument. I seems perverse that the onus on safe play is arbitrarily reversed in this situation.
Sometime soon a player landed on will be seriously hurt or even killed. I then expect the 12yo law makers to react by making all jumping for the ball illegal, taking a hugely exciting aspect out of the game.
Far better, we ask referees to penalise cynical taking out of players in the air and accept that accidents will happen in fair contests. We should be putting the onus on jumpers to be aware of players in their landing zone and to accept the risk that if they jump into an opponent then they may come off the worst.