That's a fair point, and I think you're giving a good example of a certain context of established-expert wrt beginner and how to treat it.

FWIW, I had a friend indicate that because (tenured?) teaching positions are such high demand, that the available candidates can be significantly high caliber. So that might have played into why the math professor was adversarial initially.

The area I've found the depress-to-impress used was usually in peer contexts and didn't have any teachable outcomes, unfortunately. They're regurgitating material that they have better familiarity with, but probably unable to ad-lib off their "beat path".