Even if you ignore the improvement in overall brand consistency, as a general workflow it’s a huge win. It’s basically a design framework for a large team, no different than React is a UI library for manipulating the DOM.

But as others have suggested, there’s a subtext to a UI that is not immediately logic based, and this is where a coalesced design sensibility has a strong impact. Visual affinity is constructed through a base need, and there are billions of background calculations happening to resolve this before your conscious kicks in. Saying that each change is minuscule is a first level pass at something that while useful is ignoring the full depth to the mental model of comprehension.