I assumed that shooting was a factor in free throws, but I don't really know.
FG% for top 14 FT% shooters of all time:
Mark Price - 47%
Rick Barry - 45%
Steve Nash - 49%
Peja Stojakovic - 46%
Calvin Murphy - 48%
Scott Skiles - 44%
Ray Allen - 45%
Reggie Miller - 47%
Chauncey Billups - 42%
Larry Bird - 50%
Bill Sharman - 43%
Jeff Hornacek - 50%
Ricky Pierce - 49%
Terrell Brandon - 45%
Granted, the FG% will be vary between many players because some took more 3 pt. shots than others, and and there are some generational factors that could be at play, too. But it seems that how well players shoots from the floor, even for outside shooters (notice that the top FT% shooters of all-time all are known for outside shooting, even though some could drive or post-up, too) does not necessarily translate into free throws. The highest percentage shooters are usually big players relying on inside shooting, which is a different skill.
My assumption is that in this game, the shooting skill is a general factor that applies to all shooting, inside and outside, and factors in to inside shooting skills (post moves, etc.) and outside shooting (long-distance shots), but probably mostly influences the success of mid-range shots. I also assume that shooting affects free throws, since it would make no sense if a player could, say, shoot 47% from the field, 38% in 3pt shots, and only something like 70% from the FT line. But a FT category is still a factor since it speaks to the ability to concentrate from the line. A player with a high FT skill rating, but low shooting rating is still probably not a good free throw shooter. I wonder also if height is a factor in FT shooting, since from the point of view from physics (angle, trajectory, etc), the target is a flatter ellipse for a taller player than a shorter player, which is certainly a factor that plays out historically (taller player are typically worse FT shooters than shorter players. Here's a website that gets into this:
(http://www.noahbasketball.com/make_shots.php) I'd love to here some of the development team contribute to this discussion, especially since I'm mostly conjecturing based on playing the games as an end user who's only been here for a little more than 3 months.
Don't ask what sort of Chunks they are, you probably don't want to know. Blowing Chunks since Season 4!