I also struggle with that part. the author makes it seem like guessing correctly is the logical conclusion of not having an opinion and thus not over- or under

I also struggle with that part. the author makes it seem like guessing correctly is the logical conclusion of not having an opinion and thus not over- or underestimating. One assumption is that humans can estimate at all. The average could just as well be zero, 100 or a random value. A monkey probably doesn't have an opinion about an ox, but I doubt a group of monkeys can estimate the weight of an ox. Send like there are more conditions that need to be fulfilled in order for it to work