trading cognition for pleasure seems like a reasonable example of not valuing, or failing to act on the value of, being more rational.

I think it's the same thing as before. AI drives is about a particular set of behaviors being an instrumental value for a large subset of all plausible agents; rationality is one of these instrumental (and not terminal) drives.

Providing an instance where an agent trades off an instrumental good (rationality) for a terminal good (pleasure) is simply not a counter-example - what else would an agent do when offered such a tradeoff? It would be like saying "supposedly, people earn money so as to spend it on things they want; but look! they're spending money on things like trips to Tahiti! Clearly that is not why they really earn money..."