Chocolate bar is mainly made from cacao bean, which after processed into cocoa butter and cocoa mass, then add together with some other ingredient to get chocolate, so the main ingredient is still mostly from the same raw ingredient. Compared to vanilla(extract), which is made from vanilla bean, is a flavouring that’s only meant to enhance the taste of something. So you can have vanilla bar but it will still made from something else as the main building structure of said bar, but with vanilla flavour.