"Whiteboard interview" typically does not mean "sketch a general design of a system", or the other things whiteboards get actually used for on the job. It means "here's an algorithm challenge, solve it by writing the code on the whiteboard, and we'll flunk you if you make any mistakes".

Not always a whiteboard, either; one of the best engineers I ever knew flunked a Google interview because of a situation where he had to write a bash script and read it over the phone to the interviewer, who apparently didn't transcribe it correctly on the other end. But "they only hire the best", you know, and their practices are rock-solid and proven.