Bass adding a 3 is just topping off his tank for the sale, IMO.
Sully adding the 3 primarily makes sense if he's in better shape and more mobile. If, however, he slugs up and down the court between the 3pt lines--as he appears to have largely done last night--I see his rebounds and his defense both dropping off, which is a tradeoff that I'm not too keen on.
In their current conditions, I see KO the 3pt shooter as a better rebounder than JS the 3pt shooter.