Okay, but Copilot isn't a human. It's a computer program. If I wrote an algorithm that spat out copyrighted code with the variables renamed, it would be absurd

Okay, but Copilot isn't a human. It's a computer program. If I wrote an algorithm that spat out copyrighted code with the variables renamed, it would be absurd to say that constitutes an original work. Copilot is much closer to that than to a human programmer.