Is there much reason to believe that we tend to form worthwhile intuitions from sporadic bits of evidence?

Not necessarily. But even if the intuitions were originally formed from only a couple of pieces of evidence, and plenty of confirmation bias afterwards, it still isn't going to be easy and effortless to update them to the correct level later on. (Notice also that I remarked that theoretically, the data might be exactly the same for both people, only received in a different order. That doesn't exactly mesh well with an assumption of competent updating.)