there are some artists with very strong, recognizable styles. if you provide one of these artists' name in your prompt and get a result back that employs their strong, recognizable style, i think that demonstrates that the network has a latent representation of the artists work stored inside of it.
So, what you are saying is that it is illegal to paint in the style of another artist? I‘m no lawyer, but I‘m pretty sure that is completely legss as long as you don’t claim your paintings ARE from the other artist.
That seems to indicate to me that the original work is actually not under copyright, since if it is the only method of achieving such an image in such a style, then there is no originality to be copyrighted.