> a fresh grad who prepares for 2 weeks for those whiteboard interviews will completely outclass known most productive programmers and engineers in the world (take whatever example you want, I would name someone like John Carmack) who takes the test fresh and unprepared
This extreme take is highly unlikely. World class programmers are typically extremely good in maths (and possibly have an active interest in it)/algorithms, and problem solving in general. In addition to J.Carmack (who is definitely very good in linear algebra and problem solving), another random example is F.Bellard (who calculated the largest known prime, and most digits of pi). L.Torvalds is surely extremely good with algorithms, S.Wozniak with problem solving (given his extremely good design skills in electronic engineering); another one that comes to my mind is P.Bonzini, with his 40 GB/S fizzbuzz :)
that's just the problem with these interviews. It's kind of obvious that a fresh grad who prepares for 2 weeks for those whiteboard interviews will completely outclass known most productive programmers and engineers in the world (take whatever example you want, I would name someone like John Carmack) who takes the test fresh and unprepared. The modes of thinking and toolboxes required are just entirely different.
That should tell enough about the quality of that style of interview if you are using them for anything other than to weed out people who can't code at all in a phone screen.