I think the author makes a good point.

In UI design, you're working with platforms that have limited display space, and you're working with users who have limited attention spans. To be great, you have to know what to leave out. Sure your inherent abilities in design are important, but as the number of features approaches infinity, so do your chances of designing a shitty UI.

APIs are a different story. Whether you have 10 features, 100, or 1000 is almost totally irrelevant. It doesn't affect the user experience.