> Distributing a “machine” producing such output would constitute copyright infringement.
This is the thing you haven't established.
Any ordinary general purpose computer is a "machine" that can produce copyrighted text, if you tell it to. But isn't it pretty important whether you actually do that with it or not, since it's a general purpose tool that can also do a large variety of other things?
Maybe this is a misrepresentation of the actual Anthropic case, I have no idea, but it’s the scenario I was addressing.