Show me where in the rule book it says that if you are in the lead, you are obligated to give the opposition a chance to win the game. If they don't want players to see the countdown clock, then they should have just said that, given the ump is wired up, that they should tell the player when there is, say, 15 seconds left, and call 'play on' immediately when time's up.
There will be some who say that the umps may not hear the countdown in their earpiece - simple, the guy in the earpiece does the countdown 30-29-28 and so on, and if the line goes dead, then it's up to the ump to count - which is what it always was in the first place.
This business of deciding to show the clock on the screen, then now not showing it in the last 2 minutes, all just because a North player was legitimately following the rules, makes the AFL look like a bunch of amateurs.