It's more than that. Even if you take an extreme assumption that "Full" intelligence means being able to see ALL relevant facts to a "choice" and perfectly reliably make the objective "best" choice, that does not mean that being more intelligent than we currently are guarantees better choices than we currently make.

We make our choices using a subset of the total information. Getting a larger subset of that information could still push you to the wrong choice. Local maxima of choice accuracy is possible, and it could also be possible that the "function" for choice accuracy wrt info you have is constant at a terrible value right up until you get perfect info and suddenly make perfect choices.

Much more important however, is the reminder that the known biases in the human brain are largely subconscious. No amount of better conscious thought will change the existence of the Fundamental Attribution Error for example. Biases are not because we are "dumb", but because our brains do not process things rationally, like at all. We can consciously attempt to emulate a perfectly rational machine, but that takes immense effort, almost never works well, and is largely unavailable in moments of stress.

Statisticians still suffer from gambling fallacies. Doctors still experience the Placebo Effect. The scientific method works because it removes humans as the source of truth, because the smartest human still makes human errors.