In actual fact, the underlying value may not be healthcare depending on whether the person believes healthcare maximises some confounded higher order value - i.e. health.

First of all, I think it would be a good idea to avoid use of the word "confounding" unless you use it with its technical definition, ie, to discuss whether Pr(X|Y) = Pr(X| do(Y); or informally to describe the smoking lesion problem or Simpson's paradox. I don't think that is what you are referring to in this case.

I think what you're getting at is an example Goodhart's law. See for instance http://lesswrong.com/lw/1ws/the_importance_of_goodharts_law/

Certainly, if you use prediction markets with contracts on G* instead of G, people will bet based on their true beliefs about G* instead of their true beliefs about G. In this case, futarchy will end up optimizing for G* instead of G (assuming you can find a solution to the confounding problem). I don't disagree with this criticism of futarchy, but I'm not sure I see the relevance to my post