That's a matter of perspective. AI's do not make a copy of the source material. It very much just adjusts their internal weights, which from a broadminded perspective, can be seen as simple inspiration, and not copying.
Of course, just like a human artist, it could probably closely approximate the source material if it wanted to, but it would still be its own approximation, not an exact duplicate. As for plagiarism, we all have to be careful to rephrase things we've read elsewhere, and perhaps AI's need to be trained to do this a bit better... but it doesn't change the underlying fact that they're learning from the text they read, not storing a verbatim copy (at least, no more so than a human reader with a good memory)
Of course, just like a human artist, it could probably closely approximate the source material if it wanted to, but it would still be its own approximation, not an exact duplicate. As for plagiarism, we all have to be careful to rephrase things we've read elsewhere, and perhaps AI's need to be trained to do this a bit better... but it doesn't change the underlying fact that they're learning from the text they read, not storing a verbatim copy (at least, no more so than a human reader with a good memory)