Insider trading is at least regulated in the stock market, albeit imperfectly. Imagine how much worse it would be if C-levels could just short their own stock during a board meeting. No one without insider knowledge would touch it.
Conceptually, I think that is the right analogy to think about. Prediction markets "want" to be a more accurate source of information, just like stock markets, so from that lens "getting" information to be more accurate is good. When government officials are placing bets on prediction markets, though, it's a massive violation of operational security, and leaking confidential information. They probably think that they are acting anonymously, but it creates so many opportunities for unfriendly state actors to get information, especially if people do it consistently.
The goal should be to balance the information asymmetry, not burry it.
Government officials using their power to affect war decisions ought to be a crime on it's own, not surfacing the information to the public through a prediction market.