The assumption that what's right (as in true) is what's right (as in best). It's an assumption that comes from the experience of a rational mind, as a result of braving the valley of bad rationality. It is an assumption not often shared by irrational minds (religion, etc.).

That is, if there is a brain module that is actually better off being wrong, and not just because it makes the truth easier to find, then it shows that there is a probable undiscovered alternative.

Moreover, even if that's what it boils down to, that wrong makes right easier, this will at least challenge the assumptions common among brain scientists. Those assumptions that are born from an inability to grasp beyond the dimensions of the space of their current understanding. It is an extremely common trap for practicing scientists to fall into: to forget that there is always another possibility; and if one limits oneself to knowledge related to what one is researching, then that other possibility is probably right.