well as far as i remember in other versions before switching to new type of shops , slowly all gnw characters were added in the redeem shops ( aka arena shop, survival, ranked, group etc ) so maybe that is why it sais you can get gnw choji there ( tough we don`t have all gnw chars into these shops yet .

GNW Chouji isn't implemented into the shop as of yet.

As of right now, only GNW Sakura via Ranked Shop.