I think you're interpreting the author's belief in a way that you want rather than what he actually says. I read the belief based on this statement from the ar

I think you're interpreting the author's belief in a way that you want rather than what he actually says. I read the belief based on this statement from the article: "When I released the new version, I noticed that I’d broken the autofocusing of the search field that was supposed to happen on pageload." That's it. That's the belief - he broke autofocusing when he released the new version. This was true. The later digging in to find the root cause is merely related to this belief. And yes I agree that Gettier's cases were meant to show that correct belief for the wrong reasons (maintaining the three criteria essentially), but this case meets that intent as well. The author is correct that he broke autofocus via his pull request, and thus JTB holds, but the actual reason for it is not his personal code and thus the Knowledge is incorrect.