One thing I thought when I read this is that if you only train for the competent adversary you may be unprepared for the one who is different. Could you lose if your theory of mind was wrong? But when I made a rudimentary search for this (Google is so hard to phrase, but I also used LLMs) it seems that in practice every victory is through the commander's skill in navigating their constraints. Surely,
some commander out there did a stupid thing and attacked when the rational thing would have been to retreat and it worked, or surely
someone didn't keep reserves just out of sheer incompetence and it paid off. But I can't find an example.
Either battles are uniquely unforgiving for bad strategy (entirely possible, they are usually long, which has a law of large numbers effect to it) or military historians back-form rationalizations for the victors or some other third thing I can't think of right away.
I was hoping there'd be some crystal clear example of the equivalent of not folding on an off-suit 2/7 and having it play off. But I found none. Interesting.