I disagree with #3 — I agree that anyone who values their time shouldn’t work for free. But spending 20 minutes working on something that the company is not going to use shouldn’t be considered a devaluation of the profession.
When we interview programmers, we give them a little 30–45 minutes coding test.
There are no way to tell apart someone who can talk the talk, and someone who can actually walk the walk.
Doctors and lawyers must pass exams and be certified by a board. There are no equivalent for designers and developers.