I don’t hire for technical roles, but I always ask a “how would you solve this” question. This gives me an idea about their reasoning and if they have a good grasp of similar situations. It’s not a free consulting session.

Of course, if they ask you about how you implemented the patent protected confabulator at your current role, then there’s a reason to politely decline (and they hopefully wouldn’t hire someone who spills business secrets in an interview).