And there's always a chance things go wrong, even with inside information. It would be unwise to go all in.
therefore, the polymarket betting odds will reflect the truth - even if that info is a secret that nobody else but the insider knows. And if this is the case, then even an outsider could make use of the odds as a source of info which would ensure that market efficiency (which is about the flow of information) is high.
So what's wrong with insider trading again?
Also I'm not sure how to interpret your criteria because timing matters, I don't think saying 'it gets revealed in the end' is very meaningful.
Anyway, on Polymarket specifically, sure, military strikes are a common one. Seems like a useful signal to go hide in the basement. Outside Polymarket, there were insider trades in 2008 that I'm sure were useful.
Will X country invade another before or after day X? A large enough market changes the answer, as the agent can change the decision. And we can see this kind of thing in many interesting questions.
https://gizmodo.com/checking-in-on-polymarket-bets-on-christ...