Copying entire compositions is different from references. I'm case you're unfamiliar, artists usually have a few images off to the side of their workpiece to look at for inspiration and to reference colors and image elements.
That's the thing though, a it's not uncommon for ML-generated images have major elements that are almost 1:1 copies of existing pieces, especially if the prompt includes an artist's name or a style that's closely tied to a particular artist, going well beyond an artist using existing pieces for reference/inspiration.
