TL;DR: The advent of AI based, LLM coding applications like Anthropic’s Claude and ChatGPT have prompted maintainers to experiment with integrating LLM contributions into open source codebases.
This is a fast path to open source irrelevancy, since the US copyright office has deemed LLM outputs to be uncopyrightable. This means that as more uncopyrightable LLM outputs are integrated into nominally open source codebases, value leaks out of the project, since the open source licences are not operative on public domain code.
That means that the public domain, AI generated code can be reused without attribution, and in the case of copyleft licences - can even be used in closed source projects.
I think the reimplementation stuff is a separate question because the argument for it working looks a lot stronger, and because it doesn’t have anything to do with the source material having LLM output in it. Also if this method holds as legally valid, it’s going to be easier to just do that than justify copying code directly (which would probably have to only be copies of the explicitly generated parts of the code, requiring figuring out how to replace the rest), which means it won’t matter whether some portion of it was generated. I don’t see much reason to think that a purist approach to accepting LLM code will offer any meaningful protection.
So what though? If they aren’t entirely generated, you can’t make a full fork, and why would a partial fork be useful? If it isn’t disclosed what parts are AI, you can’t even do that without risking breaking the law.