When you want a clean room non-GPL implementation of something GPL that already exists, you ask the developers not to look at the original. I don't see how this is any different.
What I'm talking about is closer to "you fire up your IDE (or Emacs) right now, and churn out 250 lines of code for some arbitrary piece of software. Is it a derivative work of every pieces of software whose source code you have previously look at?"
Note that I'm not referring to the case where the AI spits out code that is identical to code taken from another project. I'm aware that that sometimes happens, and that is obviously a problem, just like it would if a human did it. What I'm arguing is only that it probably should not be taken as a given that AI generated code is automatically considered a derivative work.
Here's a thought experiment: say an AI emits a single line of code tomorrow. You examine it, and then spend weeks, months, or even years searching all the open source code that's "out there". You fail to identify a line in any existing code-base that was clearly the upstream source for the line from the AI. So is that line a derivative work? If so, of what?
And I mean that to apply to humans as well as AI, because I'm not convinced that 'learning' is actually different in the two cases.