A fundamental part of the job is being able to break down problems from large to small, reason about them, and talk about how you do it, usually with minimal context or without deep knowledge in all aspects of what we do. We're abstraction artists.

That question wouldn't be fundamentally different than any other architecture question. Start by drawing big, hone in on smaller parts, think about edge cases, use existing knowledge. Like bread and butter stuff.

I much more question your reaction to the joke than using it as a hypothetical interview question. I actually think it's good. And if it filters out people that have that kind of reaction then it's excellent. No one wants to work with the incurious.