[crzwdjk]

That's easy enough: Google is sufficiently big and well known that even if they have an alarmingly high false negative rate, they will never run out applicants, and "weeding out" even a lot of high quality applicants doesn't substantially reduce the average competence of the remaining pool. And the company is big enough that it can absorb the occasional false positive as well, especially when it comes to people who know their algorithms but not, say, how to work on a team effectively.