What? This paragraph just seems broken. If they refuse to take a bet at 1.5:1 odds, they either have an injunction against gambling or don't actually believe there's a 66% chance, which is the entire point of the belief in belief article.

People may simultaneously have contradicting beliefs. The mind is not one unified entity: one part of it can believe in X, while another believes in not-X. Refusing the bet may simply mean that the part of them which is in control of behavior at that particular moment doesn't believe there's a 66% chance. It doesn't mean that some other part of them might not genuinely believe there's a 66% chance, and that part may be in control in other situations.