The author did have a JTB that his pull request caused the bug. The point is that we hesitate to say that he knew that his pull request caused the bug, because

The author did have a JTB that his pull request caused the bug. The point is that we hesitate to say that he knew that his pull request caused the bug, because he had the wrong justification. If you take issue with the justification, suppose that he was supposed to be the only one working on the code that day, and that the person who introduced the bug was working from home without telling anyone. He’d then have a JTB but still lack knowledge. If even that isn’t enough justification for you, then you have a problem with the entire JTB definition, and you’re essentially offering a circular definition as an alternative (since the only justification you’ll accept is justification that itself provides knowledge).