The problem is that they don't define knock on properly. If you read their definision
"Knock On: means to knock the ball towards the opponents’ dead
ball line with hand or arm, while playing at the ball."
This means that any time someone does not catch the ball cleanly and it goes forward from their body it constitutes a knock on.
THis should actually read more clearly like
"means to knock the ball towards the opponents’ dead
ball line with hand or arm and the ball makes contact with the ground, player, referee, goal post, while playing at the ball."
or something more well written.
Way too many loose interpretations, no wonder the refs get it wrong so much