Patrick
You need to realise that the word "tackle" has two meanings in Rugby Union and is used in two ways;
1. Verb: The act of grasping an opponent. e.g.
"he tackled the player around the waist";
"that was a copybook tackle"
2. Noun: a Law 14 situation where the ball carrier has been brought to ground and held by and opponent e.g.
"tackle only", "the tackled player can place, pass, push or release the ball"; "players must approach the tackle area from their own side of the ball"
The idea that a standing player whose forward progress has been halted is a "tackled" player is still a part of Rugby League Laws...
SECTION 11: THE TACKLE AND PLAY-THE-BALL
1. A player in possession may be tackled by an opposing player or players. It is illegal to tackle or
obstruct a player who is not in possession.
2. A player in possession is tackled:
(a) when he is held by one or more opposing players and the ball or the hand or arm holding the ball
comes into contact with the ground.
(b) when he is held by one or more opposing players in such a manner that he can make no further
progress and cannot part with the ball.
(c) when, being held by an opponent, the tackled player makes it evident that he has succumbed to
the tackle and wishes to be released in order to play the ball.
(d) when he is lying on the ground and an opponent already grounded places a hand on him.
...but it has not been a part of Rugby Union Laws for well over 100 years.