You say this like there is an obvious and right way to handle the situation. But the reason such a situation might end up Goodhartable is if you had three tests

You say this like there is an obvious and right way to handle the situation. But the reason such a situation might end up Goodhartable is if you had three tests every day with no time to study. Unless the requirements change, it would be impossible to "succeed" without adopting #2 or #3. This is why the GP is saying this concept is great for a top-down approach, but if you are in a system that doesn't give a shit, then you are forced to play the game or lose to those who do.