This is another of those elements of the game that is being neglected when it comes to enforcement. It sometimes results in benefit for the attacking side, whoever they are. It just needs to be picked up on now and again but maybe the problem is a that of workload for refs during that couple of seconds as mentioned earlier.
Furthermore, the attacking player with the ball pushing the marker in the chest: this should be an instant penalty. Once the tackler has moved away and the players are no longer in contact, should one of them reach out to push or pull the other, that should be an instant penalty. It would take just a few matches to stop the messing around. I'm not a big fan of being selective about which rules to pick up on or making certain infringements fashionable. All elements should be policed.....and I don't mean every occurrence necessarily, but every type just now and again. Notice in Monday night's game (hell, any game) how many times players defending their own line had both feet in the field of play by some considerable distance......
Like most of the rules in our game (and probably other sports), its not policed until something high profile happens. It had been routine for winning teams not to take the ball up with any great agression in the last set of six. Chris Joynt does it in a final and its out and out cheating. I suppose you have to commend coaches and players for noting something to exploit for a period of time, until it becomes widely known and then it clamped down.