You're making the same error in comprehension that the research paper did in it's experimental design but they at least acknowledged the limitation of their design. Your error is in assuming that the metric of employee quality is comprehensively accounted for on a resume. There is a large body of economics literature which addresses unobservable skills:
Originally Posted by teamosil
Inequality and ability
This paper examines how much the increasing ‘‘residual inequality’’ in the United States can be explained by increasing returns to cognitive skills. Also, this paper uses selection-correction techniques to estimate the latent population distribution of unobservable skill
within three occupational sectors, and breaks down the leftover ‘‘residual’’ term into a ‘‘general’’ unobservable component and a sector-specific unobservable component. The results indicate that sector-specific skills have played only a minor role in the inequality trends.
Increasing ‘‘residual inequality’’ is mostly characterized by an increasing importance of general skills, either IQ or the general unobservable skill,
within all three occupations.
No, the employer has SOME qualifications right in front of him. Those qualifications are not equalized on the issues that the researchers noted form the basis of the stereotypes that the employers reference. Those fake resumes in the experiment did nothing to equalize information on each candidates reliability, pliability and willingness to work hard. Those factors are important to employers and they were not controlled for by inclusion of relevant metrics in the resume. For instance, each employee could have come with a letter of reference which sang their praises on those three metrics. That type of information, when in the possession of a black applicant, specifically deals with that INDIVIDUAL'S attributes and that information invalidates the general stereotype. NOW, if an employer disregards the very specific information about the individual and instead relies on the general information for the group, information which he now knows doesn't apply to THIS individual, then he is guilty of racial discrimination, and that is only if his decision rests on how he valued that specific information.
But in reality the employer has the qualifications right in front of them. They see that the two applicants are exactly equally qualified, so at that point, race is no longer a useful predictor.