Exactly - advantage keeps being referred to, the rule (127) has no words relating to gaining an advantage. Boro will say (after the game ended nil nil) we had to change our tactics because of spying - that cannot be proven one way or another. We will point to them not scoring when they totally controlled the first half and had 21 shots. They will say that’s because our defence was aware of stuff they had been practicing and so it would go on as none of it can be proven and so if would go on.
the rule is about observing and that is a yes or no answer.