Need to know when he had his last negative test. Given how sensitive(perhaps over-sensitive)the tests are, hard to imagine testing negative while being infectious. Remember that the Duke player was supposedly a bench player, so not sure how close would’ve gotten to the ref. Also hard to see how he would catch it and be contagious within 24 hours. Period is usually 48 hours between exposure and being infectious. If he tested negative on Sunday, it’s really hard to see him having transmitted it to anyone in the ACC on Thursday.
My guess(and this is all a guess) is that someone in Greensboro spread it to a few people, someone who has close contact with multiple players/refs yet evaded the protocol.