I've been finding co-pilot really useful but I'll be pausing it for now, and I'm glad I have only been using it on personal projects and not anything for work. This crosses the line in my head from legal ambiguity to legal "yeah that's gonna have to stop".
I suspect he has a different problem which (thanks to Microsoft) is now a problem he has to care about: his code probably shows up in one or more repos copy-pasted with improper LGPL attribution. There'd be no way for Copilot to know that had happened, and it would have mixed in the code.
(As a side note: understanding why an ML engine outputs a particular result is still an open area of research AFAIK.)
If your standard is “Github should have an oracle to the US court system and predict what the outcome of a lawsuit alleging copyright infringement for a given snippet of code would be” then it is literally impossible for anyone to use any open source code ever because it might contain infringing code.
There is no chain of custody for this kind of thing which is what it would require.
So in this case copilot just looks at the situation like that someone gifted me this, and does not question if the person gifting was the real owner of the gift.