In the back rule

[sprockets]

The rules are clear. To give away a free kick you have to push someone in the back. It's not a free if you push or bump them in the butt, even if the player falls forward, or for any other reason than you push them in the back. It's out of hand the amount of frees given for a push in the back when it simply didn't happen.

"Legal Tackle or Legally Tackled: a tackle by a Player where:
(a) the Player being tackled is in possession of the football; and
(b) that Player is tackled below the shoulders and above the knees.
For the avoidance of doubt, a Legal Tackle may be executed by holding
(either by the body or playing uniform) a Player from the front, side or behind,
provided that a Player held from behind is not pushed in the back.

And...

17.3.2 Free Kicks - Prohibited Contact
A field Umpire shall award a Free Kick against a Player when that Player makes
any of the following Prohibited Contact with an opposition Player:
(a) executes a tackle that is not legal;
(b) pushes an opposition Player in the back;
(c) makes high contact to an opposition Player (including the top of the
shoulders) with any part of their body;
(d) holds an opposition Player who is not in possession of the football;
(e) executes an illegal Shepherd;
(f) Charges an opposition Player;
(g) trips or attempts to trip an opposition Player, whether by hand, arm,
foot or leg;
(h) kicks or attempts to kick an opposition Player;
(i) Kicks or attempts to Kick the football in a manner likely to cause injury;
(j) strikes or attempts to strike an opposition Player, whether by hand, fist,
arm, knee or head; or
(k) bumps or makes forceful contact to an opposition Player from
front-on when that Player has their head down over the football.

And...

17.5.2 Free Kicks - Marking Contests
A field Umpire shall award a Free Kick in a Marking contest against a Player
where the Player:
(a) pushes or bumps an opposition Player in the back, unless such contact
is incidental to the Marking contest and the Player is legitimately
Marking, attempting to Mark or spoil the football;

17.3.3 Permitted Contact
A Player may use their hip, shoulder, chest, arms or open hands, provided that
the football is no more than five metres away from the Player and the Player
does not make Prohibited Contact as per 17.3.2 above."

It's absolutely clear that to get an 'in the back' free kick the player must be pushed and it must be in the back. If someone dives forward when being tackled and the tackler lands on his back or touches his back due to being pulled forward in that tackle it's not a push.

 

[Strahany]

The intent of "push", in this context, is equally applicable to pushing with the legs. If you are to tackle a player, directly behind, and then drive them forward, then that is equally a push, and ultimately looks very similar to when the tackled player dives forward. The idea of the rule is that bringing the opposition player to the ground with forward momentum is not only too easy (since they're often sprinting forward, already) but is also more dangerous for the tackled player, so simply reducing "push in the back" to necessitating the arms would not be a good idea, IMO.

The umpires just need to get better at spotting these dives, and/or the AFL needs to consider retrospectively fining/suspending players who are shown to have dived/flopped in a match-review setting. This rule, like a number of other rules in our game, is only as good as the adjudicating umpire.

 

[sprockets]

The intent of "push", in this context, is equally applicable to pushing with the legs. If you are to tackle a player, directly behind, and then drive them forward, then that is equally a push, and ultimately looks very similar to when the tackled player dives forward. The idea of the rule is that bringing the opposition player to the ground with forward momentum is not only too easy (since they're often sprinting forward, already) but is also more dangerous for the tackled player, so simply reducing "push in the back" to necessitating the arms would not be a good idea, IMO.

The umpires just need to get better at spotting these dives, and/or the AFL needs to consider retrospectively fining/suspending players who are shown to have dived/flopped in a match-review setting. This rule, like a number of other rules in our game, is only as good as the adjudicating umpire.

But that kind of thinking causes confusion and is what's wrong with umpiring. There's no intent or context (or interpretation) required, the rules clearly say the offence is a 'push in the back'. If they want it to mean something other than a push in the back they should word it that way, but the offence is a push (as you suggest, it doesn't need to be only with the hands) and it needs to be in the back. It's pretty simple, as all rules should be.