My personal data point is that I received feedback that was negative on specifically my base level of concept understanding on one out of ~7 short sections I did for a company, and it made me skeptical that it was the actually the real reason.
It was a whiteboard session on how to manage scheduling and reporting progress/success/failure information for long-running jobs to a frontend UI... which is something I had been specifically doing at my previous company for a year, and have done many times in many ways before. I took some lessons about communication and focus from it, but in my mind it showed that either that section's interviewer was not very good at evaluating candidates, or some other reason was the real reason and they chose to voluntarily tell me something else as a cover instead.
I'm assuming the former, because I never asked nor expected a specific reason for rejection - no cover was necessary. Finding out just frustrated me further - I really wanted that job, and of course you can't go back saying "Maybe someone else should give that section? I think I'm really good, trust me, the guy you just rejected!"
It was a whiteboard session on how to manage scheduling and reporting progress/success/failure information for long-running jobs to a frontend UI... which is something I had been specifically doing at my previous company for a year, and have done many times in many ways before. I took some lessons about communication and focus from it, but in my mind it showed that either that section's interviewer was not very good at evaluating candidates, or some other reason was the real reason and they chose to voluntarily tell me something else as a cover instead.
I'm assuming the former, because I never asked nor expected a specific reason for rejection - no cover was necessary. Finding out just frustrated me further - I really wanted that job, and of course you can't go back saying "Maybe someone else should give that section? I think I'm really good, trust me, the guy you just rejected!"