Hello Michael and Welcome,
Aside from adding flavor, I don’t have a fact-based reply for you. But I did a little research. I hope this is what you are looking for:
This article discusses fats in baking, not specifically cocoa powder:
During the baking process, fat performs a multitude of chemical functions, such as tenderizing, leavening
This article discuses cocoa powder:
Cocoa Powder 101
How to choose the correct type for your baking needs
Cocoa powder is a common ingredient in many classic baked goods including cakes, cookies and brownies. What many people don’t know is that there are actually a couple of different types of cocoa powder available in the bulk food aisle that will give baked goods an array of different chocolate tastes.
Before cocoa powder can be made, cocoa beans must be harvested and turned into a product called cocoa liquor. The liquor then undergoes processing to remove a majority of the fat (cocoa butter) from the product. What’s left at the end of the extraction process is known as “cocoa press cake” which is then ground into the fine cocoa powder that you’ll find lining your grocery store shelves. While processing removes most of the fat content, many cocoa powders still contain at least 10-12%.
The fine cocoa powder that is left after undergoing the processing method above is known as natural cocoa powder. In some cases, the powder is alkalized, which is an additional processed used to raise the pH levels of the powder to improve its color, taste and functionality. The alkalized powder is sold as Dutch processed or Dutch cocoa powder.
The differences between natural and Dutch processed powders include taste as well as functionality. Natural cocoa powder is most commonly used in cakes, cookies and brownies because it gives baked goods a deep, rich chocolate taste. Natural cocoa powder is an acid, and when used in recipes with baking soda it will create a leavening action that causes the batter to rise in the oven. The Dutch processed powders are a neutral substance and will not react with baking soda; therefore it must be used in recipes that call for baking powder or other acidic ingredients in order to produce desirable baked goods. Dutch powders will give your baked goods a subtle chocolate flavor.