The equivalence I’m proposing isn’t between results or actions, but the causal springs of the actions. In your example, the children making legal chess moves are only doing so by luck—the causal chains determining their moves at no point involve the rules of chess—whereas the adults playing chess badly are doing so by a causal chain which includes the rules of chess. If you changed those rules, it would not change the children’s moves, but it would change the adults’.
The equivalence I’m proposing isn’t between results or actions, but the causal springs of the actions. In your example, the children making legal chess moves are only doing so by luck—the causal chains determining their moves at no point involve the rules of chess—whereas the adults playing chess badly are doing so by a causal chain which includes the rules of chess. If you changed those rules, it would not change the children’s moves, but it would change the adults’.