Tech folks often complain about the interview experience but a big part of that experience is created by tech folks. Stuff like what you went through is really to blame in tech culture imo
I WILL stumble because it's not the kind of thing I do. That's the kind of thing a fresh college grad would have memorized and can vomit it to you, maybe without even understanding it. Maybe I'll code you a basic WebRTC conference call app, or train a simple image classifier, or outline an architecture of a massive system for you?