I didn't realize how bad this Google/Facebook cargo-culting had gotten until looking for a new job the last few months (I'm approaching my 9th year in the industry). It's quite pervasive.
However, my brain froze at the time of the interview. Because I was furious. Because the interviewer kept asking me "Are you sure you have not seen this question before already?" and I kept saying I hadn't. So here is what she was actually conveying a) she does not trust the candidate b) actually having seen the problem before would have made the solution much easier (does it mean not having seen it before would make it that much harder?). Most interestingly, I later saw that the solution basically hinged around a specific insight, in other words it was a fairly binary outcome: you either figured out that little insight, or you didn't. It was not exactly a question which could have been progressively solved, and of course this brilliant interviewer was not moving on to another question either. I should have given the interviewer a piece of my mind, but unfortunately I was brought in for the round of interviews by referral from a friend.
"How Would You Move Mount Fuji?: Microsoft's Cult of the Puzzle -- How the World's Smartest Companies Select the Most Creative Thinkers" https://www.amazon.com/How-Would-Move-Mount-Fuji/dp/03167784...
which discusses the use of these types of puzzles and the expectation that they are good interview questions.
Or maybe it is totally failing at that, I have no idea. But I wouldn't dismiss it out of hand.
Even if I were to do something like machine learning I'm much better off just using something made by others, simply because developing the actual algorithms requires people completely immersed in just that and a big love of math (and the Ph.D. to go with it) much more so than programming.