How do you know whether SATs are more or less fair than GPAs? There are many opportunities for bias to impact GPAs, for instance; the SAT by its design has very few.

No doubt SATs are flawed to some extent--but shouldn't the question be whether they're more flawed than other metrics? For instance, there's a long history of outright exclusion of non-white people from all sorts of schooling, and biased evaluations when they were grudgingly let in.