The author seems to view the hiring statistics she cites as evidence of "bias", but I didn't see any attempt to control for the actual quality of the applicants. I.e. You could read all of this as just more evidence that the "system" works: the good schools tend to be enriched for good graduate students, who then tend to get a lot of the tenure-track jobs.
Then, I think we have to continue reasoning, why do those grad-students grow up and find they can only acquire tenure-track jobs by jumping to lower-tier institutions, where their own academic "children" will be considered inferior?