The headline literally says the line is being inserted regardless of usage, which makes it easy to argue that it’s entirely meaningless as an indicator of AI use at all.

One would be completely wrong.

AI is a tool that may make copyright violations more likely, but whether the output violates copyright is a property of the output, not how it was produced.

If you copy and paste leaked closed source code or if your AI produces it verbatim, you're in trouble either way. Change it up a bit and you're fine in practice in both cases.

Yeah the current guidance from US copyright office is that if it were said to be solely authored by copilot it would not be eligible for copyright. If it were said to be solely authored by human A (who happened to use co-pilot) the elements and arrangement of it not generated by co-pilot would be copyrightable. I’m not sure the copyright office has released guidance on attempting to register AI as a co-author I assume the registration would be rejected but you’d be able to re-submit as sole Human author.