Here is a brief summary of the development of the law on knock-ons.
[LAWS]1871
Knocking on i e deliberately hitting the ball with the hand and
Throwing Forward ie throwing the ball in the direction of the opponents' goal line are not lawful.[/LAWS]
1883 the word "deliberately" was removed. It didn't actually matter much since the only sanction in those days was a scrum. I don't know how strictly "deliberately" was judged.
[LAWS]1959
A knock-on occurs when the ball is propelled by the hand or arm of a player in the direction of his opponents' dead ball line or when the ball after striking the hand or arm of a player travels in the said direction; provided that a movement of the ball in the player's grasp which is in the nature of a steadying or re-adjustment of the ball within his possession without loss of control is not a knock-on.[/LAWS]
First relaxation of the definition.
[LAWS]1979
A knock-on occurs when the ball travels forward towards the direction of the opponents' dead-ball line after:-
- a player loses possession of it, or
- a players propels or strikes it with his hand or arm, or
- it strikes a player's hand or arm [inserted in 1992: and touches the ground or another player before it is recovered by the player.]
NOTES (2) If the knock-on or throw forward is
unintentional, a scrummage shall be formed [...] unless:-
- The ball is knocked on by a player who is in the act of charging down the kick of an opponent but is not attempting to catch the ball, or
- the ball is knocked on one or more times by a player who is in the act of catching or picking it up or losing possession of it and is recovered by that player before it has touched the ground or another player.
[/LAWS]More or less modern
I think it is clear that allowing deliberately knocking the ball forwards was NOT intended to be part of the relaxation.
