I think they just want LLMs to read the docs they began shipping[0] along with the library instead of using their own knowledge. For example, when I used Next.js a few months ago, models kept using cookies() and headers() without await, because that's how older Next.js versions worked, but modern Next.js requires await. I imagine there are more cases like this.

[0]: https://nextjs.org/docs/app/guides/ai-agents#how-it-works