It's not different. What I'm saying is your ability to predict Z is contingent on your ability predict X and Y. If X and Y happen to follow regular patterns,

It's not different. What I'm saying is your ability to predict Z is contingent on your ability predict X and Y. If X and Y happen to follow regular patterns, then you can predict Z, if not you're out of luck. The point is that claiming that something is not science on the grounds that it can't predict Z makes no sense.