Giving Claude or copilot attribution plays into the narrative that LLMs are more than just random word generators and that they can be ascribed authorship... I think it's a deliberate strategy so that when there's inevitably a massive copyright case MisAnthropic etc al can say "but looks at all the code co-written by Claude on GitHub" to try and convince the judge.

Just imagine building a house and saying "well I didn't do it on my own, my concrete mixer, toolbelt and coffee machine all helped!"