Maybe this is what you were looking:
http://espn.go.com/nba/draft2015/in...el-frazier-dangelo-russell-top-shooters-draft
It's part of an Insider article, but here's the relevant passage:
There is less variance in FT% than in 3P% from season to season even when looking at a similar number of attempts in each category, so there is more to it than just sample sizes.
As you mentioned, it makes sense that FT% is a slightly better predictor of NBA 3P% because it gives a decent gauge of shooting mechanics and repeatability, but without all of the variables involved 3-point shooting: contested vs. uncontested, off the dribble vs. off the catch, location on the floor (despite the uniform distance on the NCAA 3-point line, individual players just shoot better from certain spots on the floor), distance of the shot, etc.
As Pelton notes, FT% and 3P% combined only explain a quarter of the variation; that's not a bad starting point for evaluation, but that's where you have to dig deeper into those other factors. For example, you have to look at some of the stuff I just mentioned, such as their numbers off the catch vs. off the dribble, contested vs. uncontested, shot selection, etc., compare those numbers to the film, and consider the player's role in his college offense to what it's expected to be in the context of an NBA offense. For example, did the player take tough shots because of poor decision-making, or was it the offensive system and/or the players around him (i.e. lack of creators) that put the onus on the player to force some bad looks?
For Cousins, I'd love to see his off the dribble vs. off the catch. The latter is going to be much more relevant, as I'm guessing NBA teams are looking at him as an off-ball, catch-and-shoot guy. There aren't a ton of guys in the NBA who are dangerous 3-point shooters off the dribble, and those guys typically get the space to take those shots because they have the ability to blow by defenders. I don't see Cousins as a primary ball handler in the NBA, let alone regularly beating NBA defenders off the dribble.