What would be more interesting is this: are the researchers in the 80% category as productive as the researchers from the 20% of elite institutions category (on average)? This could be studied and measured, and would go a long way toward dispelling the notion of prestige.

I see what they are getting at - yes there needs to be more diversity in academia and education needs to be more available, and widely distributed, across society. I don't see however, how this is going to motivate hiring committees to take an otherwise promising, and competitive person from a lower prestige institution, who is almost certainly competing with an equally qualified person from an elite institution. Making the case that this person would also be a very good bet might help.