A whiteboard interview is (for me) never about programming or a personality exercise. The section I lead is true full-stack (drivers all the way up to presentation layers), and we own every mission critical piece of tech for one of the biggest consumers of bandwidth in the world. I really just want to see their mind work.
I fully understand that 99% of people that I am interviewing are nervous, and that nervous people forget things, or are so worried about looking stupid that they do stupid things. No matter how at ease you try to make someone you can only do so much.
I really just want to see how they go about problem solving. Pseudo code is fine, mistakes are OK. If they are very junior I want to see how well they take feedback and incorporate it into their solution. If they are senior I want to see how many novel solutions they can explain to me in a clear manner.
Everything else; languages, concepts and standards, me and the team can teach them. My team is full of intelligent folks who excel at team work and learning new skills.