The one that gets me combative is the suggestion to do some low-level optimization to make it run a tiny bit faster. My answer:
Yes, I’m sure I could, but I won’t. Optimization increases instability and since the great majority of code is response to user events, optimization is wasted time.
I go on to say that I optimize at the level of design, not by breaking rules in code.
Not that I would ever do a whiteboard interview ever again. Or work onsite ever again.
But, yeah, asking about specific knowledge is nuts. Last year I took a cryptography gig where in addition to learning libsodium and Tanker I had to pick up three new languages. Learning is part of the job, always.
Most interviewers really suck.