He was talking aboout the time around Unreal Tournament 2004, and at that generation, it was a big thing (kinda like waving grass was at one time).

Sorry, I don't recall which interview (and it would be hard to google unless there's a transcript). It might have been one of his keynotes, perhaps the one with Rage on an iPhone. I'm pretty sure it was a long one (at least 1.5 hours). It was one of the big popular videos on HN/r/programming (not an esoteric one).