Exactly. If the special non-merit criteria were instead "likes trains" or "has a monobrow" it would have the same effect. Not because those traits are negativ

Exactly. If the special non-merit criteria were instead "likes trains" or "has a monobrow" it would have the same effect. Not because those traits are negatively correlated with being good at the job, but simply because those traits are unaligned with the job, so statistically its unlikely for the best candidate to just coincidentally happen to also have those special traits.