This is basically like rebounding in basketball. You aren't allowed to cross the line to start to rebound until the ball leaves the players hand. You make the call as a player and if the ump disagrees with what you do there are consequences.I think they should remove the delay altogether and let the player on the mark follow the player with the ball.
If they play on the umpire calls it but if they are happy the player on the mark only moved once the ball player went then it doesn't matter if the call was out yet or not.
The main downside with this is it's a high risk manoeuvre to think that the player has left his mark and has played on - as it costs you 50m if the umpire doesn't agree with you.
No doubt under this interpretation we will get pinged for 50m where the opposition has run past our man on the mark and then our player decides to give chase but the ump wasn't 100% convinced that the laws of space time applied due to triangulation from the arc and the voices in their ear asking for a penalty to be applied. We then roll our eyes in disgust and its 100m for insubordination/disrespect.