I think coherence of unclear kind is an important principle that needs a place in any decision theory, and it motivates something other than pure updatelessness. I’m not sure how your argument should survive this. The perspective of expected utility and the perspective of updatelessness both have glaring flaws, respectively unwarranted updatefulness and lack of a coherence concept. They can’t argue against each other in their incomplete forms. Expected utility is no more a mistake than updatelessness.
I think coherence of unclear kind is an important principle that needs a place in any decision theory, and it motivates something other than pure updatelessness. I’m not sure how your argument should survive this. The perspective of expected utility and the perspective of updatelessness both have glaring flaws, respectively unwarranted updatefulness and lack of a coherence concept. They can’t argue against each other in their incomplete forms. Expected utility is no more a mistake than updatelessness.