The article isn't even telling half of the story, though. We only know his perspective on the actual interview, which includes his brain's attempt to explain what he perceives as failure, and we have no idea about the nature of the hiring process or what the other candidates looked like.

At some companies, you can apply for a position, go through the entire interview process, and then a company-wide hiring freeze can kill it dead. Sometimes you might be up against an internal applicants with huge advantages. The interviewer might have had a hangover. There are so many things you just can't know.

At the same time, I am a bit surprised that questions about threads and interprocess communication were challenging for a senior systems engineer with ten years experience.

The guy had taken some time off and was probably rusty.