I think his point was that, not knowing the strategy gives the strategist an advantage and the adversary a disadvantage. Once used the adversary is the wiser for the experience.
Unfortunately we on HN do not like generalization and the poster used anyone, in which he probably meant a good deal or a majority. I would note though, that anyone that is able to fundamentally change their character, to not exude intelligence, is probably not a one trick pony. He was the only experience with a person that cunning, but to me it seems like his character would be a prerequisite.
