Having read a lot about chocolate and how it's made, I have always thought that its how the nibs are roasted, once the cocoa beans have been picked, fermented and dried, and the specific temperature that is chosen to bring out the flavor of the roasted bean, that is the biggest secret to good, rich, smooth flavor.  I base this thinking on my own venture into roasting coffees, and grinding them, then brewing them at a very high temperature.  If I leave the brewing process for just 30 seconds too long, the entire pot of coffee tastes of bitter oil.  By the time the harvesting process of chocolate has gotten to the paste stage, just before they add something to help it keep its shape, the flavor is pretty well established,  They add coca butter, sugar, milk and all that, for sure, but if the initial nibs are not correctly roasted and dried, whatever is added, would not be enough to make it taste delicious.