> a class filter initially designed to not be a class filter: rich people can afford to study for months for free. Poor people can't.

I think whiteboarding problems can be silly but....

If you are applying to these jobs you either just graduated, in which case you just spent 4 years finding time to jump through all the hoops the professors gave you, surely you can find another 3 months to become an expert on whiteboarding problems.

Or you're a professional software developer. And the number of professional software developers who are good enough to work at Google or Amazon, live in the U.S. and are "poor" is a vanishingly small number.