Without knowing the ins and outs of the FIFA mechanism, and perhaps taking more a common sense approach I've got a slightly different thought.
Though in my opinion the referee was incorrect in his decision, would sending him home be the best course of action? To get to this level FIFA have obviously seen him as a ref with potential, and potentially he may not use VAR on a regular basis (apologies not sure of his full background).
Though there may be high prestige to winning, I've always seen the under age tournaments as a training ground for both players and officials, so I think getting one (admittedly KMI) wrong in a first game to be should't prevent being appointed to a second, it may well beanother game at this level with VAR may assist the referee's development. If they send him home on the back of one mistake, then potentially he could still be the best option for next summer's Under 19 or under 20 tournaments and will still have just have the one game with a bad outcome in his mind.