The confusion is resolved if you realize that both A and B here are mental simulations. When you observe the ball moving, it allows you to discard some of your simulations, but this doesn’t affect the past or future, which already were whatever they were.
To view the ball as affecting the past is to confuse the territory (which already was in some definite state) with your map (which was in a state of uncertainty re: the territory).
The confusion is resolved if you realize that both A and B here are mental simulations. When you observe the ball moving, it allows you to discard some of your simulations, but this doesn’t affect the past or future, which already were whatever they were.
To view the ball as affecting the past is to confuse the territory (which already was in some definite state) with your map (which was in a state of uncertainty re: the territory).