That is so subjective that it should be ignored. I've interviewed people who interviewed very well but in practice they failed at basic computer programming concepts and implementations.
We simply do not have an objective measure for program quality and thus do not have an objective measure for programming aptitude.
In the face of this problem we can either give up and not try to measure anything, or we can use an obviously subjective measure and understand where the weaknesses are.
I've interviewed and worked with many people, MANY!, including e.g., Stanford MS CS graduates, who can't write real-world apps. I assume these people can score well on an algebra test. As far as I know, the ability to write non-trivial programs in a commercially relevant time frame can only be judged based on a candidate having already done so. If there's otherwise some way to predict who these people are, I'd love to know what it is.
Social factors in a workplace also seem to be important and hard to predict. Excellent work for one employer isn't necessarily reproducible for another.
These instructors are spending all day, every day with the students as teachers lecturing and helping them through exercises. They're not interviewing them.
In the face of this problem we can either give up and not try to measure anything, or we can use an obviously subjective measure and understand where the weaknesses are.