The skills your game tests and the moves available to players must be aligned.

Said another way, their possible moves should relate to the skills that the game is rewarding them for mastering. This is where a clear definition of relevant skills comes into play.

Consider a game where the key skill is predicting the opponent’s plays accurately.

You could give players moves that increase the reward for a correct prediction, or which reduce the opponent’s reward for picking a specific option—these moves support the key skill by changing the risk/reward proposition.

But a move that lets you see your opponent’s play then make your play doesn’t support the key skill—it circumvents it. Likewise, a move which just gives you a few points without needing to make any prediction would do the same.