>t is next to impossible to prove a candidate was rejected on the basis of race

It is possible to prove a company is disproportionally one or the other when making the claim. Of course when an industry has far less applicants or members of a certain group that's to be expected but still. Consequentially I've heard of some pretty blatant race based selection especially in the US. It's just that that selection ends up excluding white people (or east asians) A while ago I even discussed with a hr person here on hn who was defending their hiring of that sort with the most flowery wording about 'just giving priority' or 'reaching out to members of their prefered group specifically' fist if all they get is not the desired group.