Eh, NCAA basketball is also full of grown men these days.
The Big Ten is probably a step up in competition from the ABA. If you look at ABA rosters, yes there are more experienced players, but not a lot of guys who have the talent/athleticism of a high-major starter. It's certainly a higher level of competition than high school level in the US - probably more akin to a low major. At the same time, guys like the Ivisic's and Mirkovic are young, developing, improving players. So I think it's really hard to project out what ABA stats will translate to in NCAA/Big Ten play.
Tomi's 3pt% went down from 42% in ABA to 36% in NCAA, as a point of reference. Probably at least in part because of better defenders. On the other hand, Big Z's went up. Probably because he's a young player who is improving.