Yes, the core idea of looking for someone who neither says they can do something difficult really simply nor says they can't do it is sound.
It's the idea of requesting the contractor to give feedback on a task that you have no intention of having them complete that people (including me) are taking issue with.
The title of the test is irrelevant - the test could easily be asking a contractor if they could develop an application that does abc in such-and-such a time-frame then turning round and telling them "I don't actually want an application that does that, I just wanted to see what you'd say".
It's the idea of requesting the contractor to give feedback on a task that you have no intention of having them complete that people (including me) are taking issue with.
The title of the test is irrelevant - the test could easily be asking a contractor if they could develop an application that does abc in such-and-such a time-frame then turning round and telling them "I don't actually want an application that does that, I just wanted to see what you'd say".