The theory used here though is that fair use permits transformative use. Normally copilot output should be sufficiently transformative. This particular situation appears to be a sort of bug (overfit).
Note that AI models already work somewhat similarly to how humans work (becoming bug-for-bug compatible at times even :-P ). We may need laws to be amended in the opposite direction even, else it might become illegal for humans to learn too.
Of course everything a human learns and produces is a derivative of real world input, some of it copyrighted. But people agreed that this transformation is a form of fair use, as long as the derived work is sufficiently creative - where the key implicit assumption is that creativity is a human ability that warrants protection. Both the creator and the learner enjoy protection because they are human.
In the AI case, the output of a program will certainly not receive protection by default - it will be protected only as a consequence of its human creator or user rights. It doesn't really matter how transformative and analogous to the human mind the program is, the output only deserves protection solely for its unique human created parts - the internal working and the extent of the craft embedded in a GPT3 text prompt. The first is unrelated directly to the work produced, and the second is laughable vs the artworks embedded in the model.
If in the future AI advances to the point where it can be granted natural rights, this could change, but we are far far from that point.
Animals have (some, limited) natural rights, but can't hold copyright. Corporations don't have "natural" rights but can hold copyright.