The short answer is that this is a slippery slope argument. The long answer is: In this hypothetical future where 95% of the Linux kernel is AI generated, it stands to reason that generating an OS kernel is possible (by definition of the hypothetical). If generating a full OS kernel is possible then people could generate a fully closed source kernel without using any of the 5% of GPL protected code in the Linux kernel. If you allow that it's possible for AI to create a kernel with AI generated code then it will happen regardless of the status of the Linux kernel's copyright protections.