It's the same interpretation as Thaidays no try in Origin 2 2014. Hayne dislodged the ball from Thaidays grasp as he was reaching out to ground it. Thaiday regathered the ball/grounded it simultaneously to it hitting the ground. The video ref (and every blues fan) adjudicated that it was a loose carry and ruled no try.
In a try scoring situation they always seem to err on the side of knock on when the ball is dislodged.
I don't know what the interpretation (official) of the Thaiday no try was, but it is nothing like the Tamou no try.
I would be happy to rule all of these no try, and say that players should hang on to the ball. I also accept that in the field of play, a lost ball due to a strip, or even a possible strip, is often ruled a knock on and often ruled play on, and it is very inconsistent, but the referee only has a fraction of a second and one look.
But the reason we are shocked at the decision is that a ball knocked out by an opponent, without having lost possession before the opponent touches it, is nearly always ruled play on when the advantage of replays can view it. I don't necessarily like it, but it is common.
The Thaiday no try could be considered similar, but there is a possibility the ball comes free regardless of if Hayne plays at it, and there was no doubt the ball leaves Thaiday's possession and travels forward.
When the ball is propelled backwards by the defender (backwards relative to the attacker), and the attacker loses it only from the ball being propelled backwards, I don't think I've ever seen that called a knock on before.
I'd be happy if it always is, but it won't be.