It wasn't a knock on yet because it was still in the air. Nightingale was well within his rights to tackle him. It's not a knock on UNTIL THE BALL HITS SOMETHING AFTER GOING FORWARD. Until that happens, the last person to touch the ball is deemed to be in possession of the ball and as such can be tackled. Again, been like this for 20+ years.
just to reiterate - if you intentionally play at the ball and hit it up in the air, you are fair game to be tackled even though you don't have the ball in your hands. If you intentionally hit it forward its a penalty, if you intentionally play at it but didn't mean for it to go forward, like hodges did, its play on and you can be tackled since you're in possession until it hits something else.
Again, show me the rule in the rulebook. Not the one you made up. By your reckoning you can tackle someone after they've passed it but before someone else has caught it. Dumbarse.