To me, it's different because having read a book, remembered it, and pulled out the quote means you spent time on it. Pasting a response from ChatGPT means you didn't even bother reading that, understand the output, thought about it to make sure it makes sense, and then resynthesize it.

It mostly means you don't respect the other person's time and it's making them do the vetting. And that's the rude part.