I disagree. Rounded rectangles are a signature Mac OS user interface feature. Thanks to post-Steve Jobs Apple, there is renewed interest in everyhing Apple, and rounded rectangles are truly everywhere. You would have a hard time finding a popular web site not using them.
What is really interesting in this story is not the algorithm itself, but how Steve Jobs convinced Bill Atkinson by taking a walk outside with him to show how common rounded-corners are in "real-life".
A story can be satisfying because of its relevance. I think that is the case here. The topic is interesting to developers who want to understand how Apple approaches design, even though the story's structure might have some flaws.
It does not matter how relevant you find some aspect of this story, it's still poorly told - and this should be especially clear if the focus on the the interaction between Atkinson and Jobs is what you consider key. Half of the story is about details of an algorithm that simply don't matter if the core of the story is Jobs badgering Atkinson into being willing to code rounded rectangles.
The background about the algorithm helps you understand why Bill is reluctant to go back and implement a new different drawing primitive. His reluctance is the reason why Steve needs to work hard at convincing him, which demonstrates the theme of the story.
I agree that it's probably too detailed in the first bit, but I don't see it as a major flaw for a series of articles about the development of the original Macintosh. The intended audience consists of hackers and developers who get intrigued by technical details.
What is really interesting in this story is not the algorithm itself, but how Steve Jobs convinced Bill Atkinson by taking a walk outside with him to show how common rounded-corners are in "real-life".