Whether or not I agree with your interpretation of that clause (I am choosing not to analyze that too deeply), the vast majority of my code isn't on GitHub because I uploaded it there... it is on GitHub because it was open source and someone else--someone who uses GitHub to manage their projects--uploaded it, whether as a mere fork or as a legitimately derived work. If you were right, and this did matter to their legality, this would thereby mean 1) that Copilot's database is already tainted and 2) that I guess GitHub isn't actually capable of being used to host GPL projects at all (which I doubt is the intention).