I wonder if this means that in a true free market betting is actually impossible as extra-gaming structures like those spontaneously emerge.

You need centralized regulation to make it work.

The standard argument for prediction markets does not include any kind of fairness in gambling. Rather, the point is precisely to surface insider or otherwise well-founded knowledge of the real odds so they can be available to anyone who wishes to look at the price.

(And I do not see how this first-order viewpoint is problematic, precisely. It’s the second-order consequences of people making the currently-considered-unlikely decision in order to cash in on a bet that I have an issue with.)