Remember, I did not ask for an implementation. Only a document with their thought process on implementing it. Also, they can use whatever means they like, if we hire them we will quickly find out if they are incompetent. No interview system is fool proof, of course.

How fast could you then fire them? How much money wasted on that and onboarding? Compared to the risk of missing out on that one person who cannot whiteboard but is otherwise brilliant? Quite a gamble.