The difference between piracy and having your content used for training a generative model, is that in the latter case, the content isn't redistributed. It's like downloading a movie from netflix (and eventually distributing it for free) vs watching a movie on netflix and using it as inspiration to make your own movie.

The legality of it all is unclear and most of that is because the technology evolved so quickly that the legal framework is just not equipped to deal with it. Despite the obvious moral issues with scraping artist's content.