I hear this all the time. Yeah, that might be true in some cases, but it's also valid in quite a lot of instances (like the example you provided).
> it is categorically impossible to establish in a 45 minute interview whether a person is actually a "fit" or not
I've run/sat in on several trainwreck interviews over the years (for ad account manager roles and logistical analyst roles mostly). Here are a few examples of candidates that were perfect in every way until the interview based on culture fit:
* The guy that mentioned he only traveled to Thailand because ladyboys do it better.
* The guy that mentioned he wouldn't work with anyone that drank alcohol because it's "the retardant of the masses". Fair enough opinion. About 20% of our ad sales came from alcohol-related businesses. I asked if he would have a problem dealing with liquor businesses. He explained that wouldn't be a problem as long as they didn't ask if he drank.
* I was sitting in on an interview with the Marketing Director for an account management gig on a Monday morning. We asked the candidate if she did anything noteworthy over the weekend. She told us she went dancing with her friend "Molly" at a music festival and laughed.
* The analyst that mentioned he scrapes NSFW subreddits in his spare time and links throwaway accounts to main accounts based on comment history, similar subreddit crossover, posting times, and vernacular (his tool was pretty impressive -- it sent him an email whenever it had a hit with over 50% accuracy or something which he received during the interview).