Thank you very much for the information. The origin of the intentional knock-on is pretty old than I thought.
I still think even an intercept attempt "looks" reckless or unrealistic, encouraging that kind of difference play will make rugby more fun and exiting rather than penalizing it.
FWIW, I think a clue for referees is
"hard hands" v
"soft hands"... or
"at the ball" v
"to the ball"
An example of
"hard hands" is a player who reactively jams an arm out
"at the ball" in order to get their hand between the passer and the receiver. They should only going get away with this if they actually end up catching the ball. If they end up knocking the ball on, then I would regard that as deliberate or intentional.
An example of
"soft hands" is a player who gets their body into position so that they can get their hand(s)
"to the ball" in order to catch it. If they end up knocking the ball on, then I would regard that as accidental or unintentional.
In any case where a player deliberately knocks the ball ahead with the intention of regathering it, and then fails to do so, I would regard as an intentional knock on
Watch the first seven intercepts in this video...
https://www.youtube.com/watch?v=ij38G6IdQZI
The first two I would say are examples of
"hard hands, at the ball". Had they dropped the ball, I would rule those as an intentional knock ons
The next five for mine are examples of
"soft hands, to the ball". Had they dropped the ball, I would just call those as knock on.