If you think that algorithms and math are not applicable to programming at Amazon, Facebook or Google's scale, you really do not understand the work that they are doing.
Being able to remember and implement those algorithms in under 20 minutes on a white board is not applicable to programming at Amazon, Facebook or Google at scale.
You said that he's studying interview techniques -- he's studying math for cs, basic algorithms, and algorithmic design. He mentioned that whiteboarding has scared him, he did not say that he was studying only to get better at whiteboarding.
My issue was more with the answers given here, not the question asked. When I wrote this comment, the top comment and all of the others recommended studying interview questions, not algorithms and math FOR answering interview questions. That's what bothers me.