I worked in the underrepresented student office, so I was keenly aware/curious about that possibility when I began. However, after reviewing thousands of applications, my experience, to my surprise, was that GPA to SAT/ACT scores remained highly correlated regardless of race. If memory serves (and it’s been awhile) the outliers who were more likely to have higher SAT/ACT than their GPA normally suggested, tended to come from predominantly non-white schools. I’ve seen so many reports to the contrary that this surprised me to no end, but that’s what I observed.