When you say plagiarizes, do you mean they are publishing their own docs without ads? Or you mean when the AI is reading the docs instead of a person they ignore the ads?
People don't just ask AI to produce a Tailwind app, they also ask AI specific questions that are answered in the docs. When the AI regurgitates the answers from the docs they don't visit the actual docs. Like the Google answer box in search results stealing clicks from the pages that produce the content.
The answer is "it depends". If someone printed out the documentation and bound it together to sell without permission? Yes. The mere act of converting from one medium to another usually isn't transformative.
The test for writing a book is whether the author applied their own judgement in the creation of the book. Even if some explanations of concepts are inevitably similar the structure of the book, the example code, etc. will reflect the author's judgement and experience.
An LLM is incapable of authorial intent. It's not synthesizing the docs with a career of experience and the input of an editor. It's playing madlibs with the work of one or more prior authors.