If you read to the end of the article, it seems the study is looking at spice use more broadly and not so much spicyness (ie. heat) specifically. That would explain why east African food that is influenced by spice trade with India ranks so high on the scale compared to west African food.
While the chili peppers originated in the New World the fact remains that they grow better in Asia than in Norway which is what people mean by 'local food's in this context.
