It's things I've interviewed for that show up in conversations. It's intellectual curiosity. It's flexible heuristic development, passion to learn, etc. IQ can be a light proxy for some of this, and as per the article grades are an even lighter proxy. Degress at least represent some incoming body of knowledge (if they can put it to use.)
This shows on IQ tests with the processing speed or working memory disconnect often shown for gifted. The more aptitudinal processing speed shows in leaps in thought with the dull and obvious bits swept under. It's not showing your work. Working memory is more interesting about how much of a puzzle can you hold in your head, how well you prop it together to hold even more.
An easy interview trick is to use a jargony acronym that you are highly confident the candidate doesn't know. Do they ask about it? Mention an interesting problem in passing, do they scoot forward in their seat, can you see them itching to want to solve it?
