But those resources are already redistributed (from a distribution that somewhat aligns with demographics) with things like personal relationships (think legacy admissions or a father's buddy handshake internship). AA is meant to correct historical instances of this which snowball into familial / generational wealth and (most difficult to diffuse) social capital that was distributed unfairly.

That's the argument for it, not my belief. The argument for AA is that the so-called meritocracy had/has its own unequal distributions.