I mean you answered yourself why it didn't work, if there is no useful data in its training corpus, it would be a miracle if it could correctly guess unknown information.
The data is certainly available, both in Linux kernel source and LKML history. The answers looked perfect at first glance; anyone without prior knowledge of kernel compilation and patching would have probably be impressed by the technical details in the answer. That's the typical LLM failure mode : it provides an answer when search engines fail you (because they provide you only the most basic, generic NFS-related forum posts while I was looking for strong technical information in a high-performance environment), but this answer isn't much better (even after pointing out the error), but would fool most people....