Yes, least optimal truths are really terrible, and the analogy is apt. You are not a perfect rationalist. You cannot perfectly simulate even one future, much less infinite possible ones. The truth can hurt you, or possibly kill you, and you have just been warned about it. This problem is a demonstration of that fact.

That said, if your terminal value is not truth, a most optimal falsehood (not merely a reasonably okay one) would be a really good thing. Since you are (again) not a perfect rationalist, there's bound to be something that you could be falsely believing that would lead you to better consequences than your current beliefs.