I'm sure there's context missing in that quote. Bar Raisers would not veto someone just because they didn't know specific things about a programming language ... unless they claim to be masters of a certain language.
I was about to say the same thing. The only reason that a bar raiser would ask the question would be if the applicant claimed to have the knowledge. If your resume claims a certain number of years of experience with a language, and you are asked how well you know it, you'd better be very confident before you say that you are an expert.
One of my favorite red flags. If you put it on the resume and I ask about it, and you've never used it, gong time. Personally I redact my resume every year from stuff I've done long ago. If you're not proficient, don't advertise it.