Hard to call that a "perfect interview process", because from individual candidate point of view, some with unusual characteristics could be unfairly disadvantaged (and other unfairly advantaged), while reaching your overall "neutral" distribution at the end. Short of being an omniscient interview process, I'm not sure this can absolutely be avoided, so in practice you have to be very careful with the kind of correlation presented here. Even if that ends up not being Berkson, but a property of all programmers.