I think this really explains much of the mystery of the 20 years of experience engineer who can't pass fizzbuzz. Writing code on paper/whiteboard is completely different from a text editor.
Just think about how you write code. You write a few lines. Run it in your head. Notice a mistake, add a newline, remove some brackets and it's all good. Oh wait, you just noticed this can be simplified. Ctrl-A delete all, reduce entire 20 line function into 5 lines.
None of this is possible on paper/whiteboard, especially in a timed interview setting. Paper/whiteboard is effectively immutable. You get one chance to write it down correctly and that's it. There's just no time and it's too difficult to even add a newline somewhere.
So you put a 20 year programming veteran in front of the whiteboard and they can't do fizzbuzz because writing code like that is so foreign to what they do. They can't just write something and fine tune it, which is how software is written. It must be perfect on the first try. they freeze up and fail.
There is zero excuse for companies to not give a laptop for interview coding. Even if it's Linux boot CD with nothing but vim and nano, that's still so much better than whiteboards. And these days companies use hackerrank during the phone screen. Just use the same website on a chromebook during the onsite!
Writing code on whiteboard is just really stupid. Can we all agree on this at least?