Simple physics Waz. If you are travelling in your car and throw something out the back, is that something going forward or backwards in relation to the car. If you are standing by the road side you will see the car travelling fast past you and then you will see what was thrown out the back also travelling forward in relation to what you are observing, but just not as fast as the car. Its going forward as you see it, but backwards in relation to the car.
The rules of the game are not what you see on the side line that appears to be going forward. The rules state it is in relation to the person running forward and passing the item in a backward motion. To him it goes backward. To you it looks forward. The rule relates to what he does, not what you observe. It could travel five metres forward as you see it, but if he is running so fast that he travels beyond that distance in the same time, the ball has in fact gone backwards. This is where commentators, refs, linesmen and so many in the public get it wrong. Its simple physics.