Well, first off, I don't subscribe to the Calipari narratives that are proffered as facts by many that post on here. "Calipari thinks ______", "Calipari's teams have to have _______," etc. It's just nonsense. Calipari will play the players and also play in the manner that he thinks will give him the best chance to win in March.
So, my guess is maybe Calipari is thinking there is an advantage he can gain with experienced upperclassmen who have developed as shooters and proven they can provide a much higher floor of play and production. I think it's just too hard and erratic to rely on freshmen for high level shooting and dependable go to scoring. Sure, when the best athletes catch up skill-wise they will be the better players, but it takes time for them to get there and they're only going to get part of the way in 1 freshman year of college. I think Calipari may think he sees an easier way with less risk by using less "talented" but currently better players (i.e., proven upperclassmen).