The purpose is to establish that "qualia" are not ontologically basic building blocks of the universe sprung into existence alongside up-quarks and charmings for the express purpose of allowing some specific subset of possible complex causal systems to have more stuff that sets them apart from other complex causal systems,

But it doesn't. It just establishes that if they, they covary with physical states in the way that would be expected from identity theory. Admitedly it seems redundant to have a non physical extra ingredient that nonetheless just shadows what brains are doing physicallly. I think that's a flaw in Chalmers' theory. But its conceptual, not empirical.