I don't disagree with what you're saying, but I was just going by what Silver said:
“My sense is it’s not working for anyone,” Silver said Thursday night before Game 1 of the N.B.A. finals. “It’s not working for the college coaches and athletic directors I hear from. They’re not happy with the current system. And I know our teams aren’t happy either, in part because they don’t necessarily think the players who are coming into the league are getting the kind of training that they would expect to see.”
Link:
https://www.nytimes.com/2017/06/01/sports/basketball/adam-silver-nba-draft-one-and-done.html
That last part is what struck me. To me, he's saying his NBA people are telling him that Calipari and the other college coaches aren't getting these guys prepared properly. Also, I realize some of these guys are doing well, but the question is whether they can and should be doing better. The NBA Commissioner seems to be saying they can and should be doing better.
I have no idea if Silver was just talking or if he's serious about a change. But it makes sense to me, that if they're unhappy with the tutelage these prodigies are getting playing in college, that they'd want to bring them into the NBA environment at a younger age.