It's a really interesting point you raise. Road not taken etc. I wonder if google quantifies the impact of hires over the long term. How productive are you? How much does your contribution make the company and if you weren't here would google notice?

If google could know when it was about to deny a speculative false negative it could hire them exclusively into a part of the company where everyone is a speculative false negative. Then you could just watch them compete with those who pass and try and measure something objective.