The two are different. A player who simply loses the ball forward has indeed knocked the ball on. The highly significant difference is that we allow a player to release the ball forward in order to effect a punt or drop kick. If we are to be consistent, we either sanction that, or we don't sanction the interrupted kick. Chalk and cheese.As far as I'm concerned if the ball carrier is tackled and drops the ball forwards then he has knocked on.
If he tries to kick and misses it then the ball has clearly gone forward. That's a scrum.
If an opponent gets to him and interrupts the kick process that becomes a knock on.
I see no problem around the opponent's action creating an offence. After all it did so in case 1 above, and I really hope that is not contested.