The fair use concept applies to any copyrighted material, I suppose.
BTW, maybe OpenAI can build on this their defence line. If they prove in court that the materials they got from Apple have never been used for design of products, and OpenAI only collected some linguistic statistics from the docs (as we know, training LLM is concepfually no different from calculating word frequencies), which does not violate copyrights. As for possible similafities in pfoducts to the Apple design, that's just a coincedence, developers can come to equal solutions when solving equal problenms. Equipped with modern AI assistants they quickly re-discover approaches others have discovered.