I had a C with great FT once (I think 15 or 16). His IS was 2 skills lower than my PF's. But many times my C took more shots because if fouled, he had greater chance to score. So great (not good, but great) FT skill could make a player to shoot more despite being surrounder by better shooters.
That's a really interesting theory, thoght I've never had a player with more than 11 free throws.
Maybe your C was a physical player and the high lvl of FT was the perfect combo.