He said there would be both an "AI kill switch" but that it's also "opt-in". Taken together, his two statements seem a little...odd.

People are already getting worked up about being prompted to opt into a new feature on update (even if that prompt is hidden behind an icon that doesn't do anything until the user clicks it), so it's not inconceivable that the kill switch just disables those opt-in prompts for AI-related features.

I guess that just means that there will be a number of AI related features you can choose to select but if at some point you want it all gone you just hit the checkmark Disable all AI.