[rssoconnor]

By this analogy, (non-local) hidden variable theories are the ether of quantum mechanics: The ether determines the true value of simultaneity, and hidden variables determine the true outcomes of measurements.

For both theories the physics surrounding them just happens to make their presence undetectable. In the case of the ether, the ether wind just happens to shrink the arms of the Michelson-Morley interferometer by exactly the amount needed to prevent the interference pattern from detecting the ether wind. In the case of hidden variable theories, the predicted joint probability distributions just happen to make the hidden variable values themselves uninferable.