This event is not mythical. That is why the log entry says "First /actual/ case of a bug being found". It's a humorous pointing out of "We've called them bugs

This event is not mythical. That is why the log entry says "First /actual/ case of a bug being found". It's a humorous pointing out of "We've called them bugs for a long time, but this time it actually was a real, physical bug, and here it is - ha ha." The myth is that people for some reason started thinking that was the first use of the word "bug" in this context.