The shooting percentages are a little disconcerting, but numbers can sometimes be deceiving. It's possible that his overall FG% is so low because a good chunk of his field-goal attempts are three-pointers. Here's a possible scenario:
2-pointers: 51/100 = 51%
3-pointers: 105/300= 35%
Combined: 156/400=39%
Effective FG%: 52.1%
I'm not sure this is the case, but if he is a high-volume 3-point shooter, that might explain why his FG% is so low.