You're overlooking that sudden, unexplained or counterintuitive movements in the actual prediction market itself, well before the event occurs/market resolves can themselves convey information, about what apparent insiders think (or whales want to manipulate the market to think).

Obvious example: Polymarket now has 69(!) markets involving Iran: https://polymarket.com/predictions/iran

Consider the timing of those markets wrt 2026 national elections in US, Israel, also Sweden, legislative elections in France, Germany (as canaries for their next general elections) plus a possible change in UK PM, plus any possible Ukraine or Venezuela outcomes. And of course events in the stock market or energy markets make certain outcomes more/less likely.

Also, on Polymarket traders often buy and sell before a market resolves, to exploit patterns in other traders.

And consider what happens at major media e.g. CNN now they've partnered with Kalshi, wrt whether the broadcasting certain predictions/viewpoints/interviewees get boosted/suppressed.

There's also a financial incentive to get your bets in early, while the odds are still in your favor. The longer you wait, the higher the risk that your secret becomes public knowledge.

I agree it's not perfect, but I think you're underplaying a lot of the value.