Imagine if lawyers could be rejected for not being able to explain the minority opinion in Foobar v. Bazquux, which again, has absolutely nothing to do with their expected duties as prosecutor of poor people with small amounts of marijuana.
Imagine if real engineers were asked to build a suspension bridge out of silly putty, table salt, and carbon fiber.
The interviewees are simply doing their jobs, which is to analyze a problem and implement the most cost-effective solution. The interviewers are the ones causing the problem. Granted, it isn't always because they are non-technical people trying to gauge the value of skills they don't understand. A lot of times, it is because the interviewer is a tech person that still can't effectively gauge the value of skills they do understand, and also wants to look clever in front of a stranger, subtly discriminate to preserve "culture", and do the same stuff to others that had been previously done to them in their interviews.
Indeed; this is a point I make over and over. HR departments aren't smart enough to detect ageism being openly practiced right under their noses...