ChatGPT is full of sensitive private information and spits out verbatim text from CNN, Goodreads, WordPress blogs, fandom wikis, Terms of Service agreements, Stack Overflow source code, Wikipedia pages, news blogs, random internet comments, and much more.
They are spitting out, as in the quote above, “verbatim text”, as in, word for word. That is copyrightable.
And that’s not what you said. You said it has no memory. That’s clearly wrong.
It’s only under copyright if it’s a significant portion of the work. Single sentences are not enough, unless it’s a short poem.