It sounds like you're agreeing with the author here, because he says,
>I fear that when large companies hire and promote people based on group identities, it discourages individuals from cultivating their abilities.
It is only one logical step to go from one to the other. The idea that the promotion process is so random that the introduction of an additional random factor (D&I status is totally uncorrelated to performance) can't make it any worse would nullify anyone's faith in performance incentives.