He probably has actual experience with branch prediction. He probably dabbled or had experience with angular in other jobs (he worked at google apparently, so maybe there).

He'll most likely be stumped if you provide a graphic problem that a graphic designer with a few years of experience would solve in an instant, or an ML problem for a data scientist with similar experience.

That doesn't mean he isn't extremely smart. He most likely is (it takes a lot of brain to do these things), but the fact that you can't tell branch prediction problems even though you had some computer architecture class in the past is irrelevant.