To an extent, I agree.

As long as it's valid questions that are stressing him out, that's fine. How does this regulation apply to?, why might you get this annunciator? Can you land with this weather? These can have several follow up questions and absolutely be good scenarios that "test" the individual, and they should. But remember, even though it IS going to be stressful, even though there SHOULD be questions that challenge the applicant, it's not a "stress test" to find out where they break either.

Hopefully that applicant is there because the company already thinks they have what it takes to be a captain. Hopefully they were hired with the idea that they could eventually make it as a captain.

The engine fire and brake questions is a great example. The good examiner like you say is looking for a well thought out and justified answer that makes sense. They aren't looking for a specific answer necessarily, because there is no "right" answer and they realize it. The poor examiner is going to have their mind made up already on what the correct answer is, not realizing they have more information in their mind to make that decision than the applicant has, and the applicant may still be answering well within the standards, it's just that it's not the answer the examiner was expecting and wants to hear. Sometimes those examiners will start to "hold it against" the applicant, and it all goes downhill from there. It shouldn't be a "hmm, he's answering these questions easily, so I need to ask harder questions".

I'm not saying this is overly prevalent, it's just an area where examiners have to be very careful to not get caught up. It's easy to say these things on paper, but often more challenging actually doing them as an examiner.