No, I mean it generally worked well. I can't really say how it worked in undergrad because grad and undergrad school were so separate. I can only talk about grad school. I was really surprised myself how well it worked because I didn't know this coming from my university in Germany, but it really did work, at least in every exam I saw. And I don't consider myself overly naive. I guess it has to do with the fact that people who get admitted to Stanford grad school have already proven a certain work ethic and really want to do the exams to learn more. Your final grade isn't as important when you graduate from Stanford; it only really matters if you want to do a PhD, otherwise it's borderline irrelevant. "I went to Stanford" is all you need for your CV. So I didn't feel a lot of pressure being there of always having to have the best grades, it was more about using your very expensive time there wisely to learn as much as you can, and I felt my peers were the same.
Now, I'm not saying every place can be like that, I'm just trying to explain why at this particular university, the honor code is a reasonable policy that may work perfectly well on policing AI in exams. You can't copy that to other institutions, but it answers how they do it here.