I must have wrote out my initial response poorly (or something was ignored), because that's not what I'm saying at all.
One and Done - Better for the NBA than the old model, because it improves scouting, reduces draft risk (as I pointed out in my post), ensures guaranteed contracts go to better players, provides free development, and free marketing.
Two and Done - Same as Above, but all the factors become even more significant. More scouting, even less risks at this point.
HS or 3 Years - Your not going to get 3 years to scout for most kids. Your going to kids like Bender and Ebi that make the jump early. Your going to get kids who would have went to school for 1 or 2 years jumping early. A 17/18 year old HS basketball kid sees the success of a few athletes at 19/20, and thinks he can do the same. Unfortunately many will flop. An MLB prospect will not see the same examples.
HS NBA prospect thinks he is choosing betweeen "Big City NBA life" or College.
HS MLB prospect thinks he is choosing between "Hicktown, USA" or College.
The model will encourage worst decisions if done in the NBA.
The 2 year minimum is much, much better for the NBA.