I agree with both your claims, but maybe with less confidence than you (I also agree with DanielFilan’s point below).
Here are two places I can imagine MIRI’s intuitions here coming from, and I’m interested in your thoughts on them:
(1) The “idealized reasoner is analogous to a Carnot engine” argument. It seems like you think advanced AI systems will be importantly disanalogous to this idea, and that’s not obvious to me.
(2) ‘We might care about expected utility maximization / theoretical rationality because there is an important sense in which you are less capable / dumber / irrational if e.g. you are susceptible to money pumps. So advanced agents, since they are advanced, will act closer to ideal agents.’
(I don’t have much time to comment so sorry if the above is confusing)
Like some other commenters, I also highly recommend Impro if this post resonates with you.
Readers who are very interested in a more conceptual analysis of what decision making “is” in the narrative framework may want to check out Tempo (by Venkatesh Rao, who writes at Ribbonfarm). Rao takes as axiomatic the memetically derived idea that all our choices are between life scripts that end in our death, and looks at how to make these choices. It’s more of an analytical book on strategy (with exercises) than a poetic exemplar of Mythic Mode, but it seems very related to me. In particular, I think it helps with a core question of Mythic Mode: how do you get useful work out of this narrative way of thinking without being led astray? I don’t claim to have an answer, but reading Tempo has certainly been useful for this question.