No, it's "learn by building things" with a very tight feedback loop.

When copying, you can immediately see where your expert has done something differently from you. And you can either learn to do it their way, or understand how different methods lead to different outcomes, and so consciously build your own style.

Building your own things is absolutely valuable. But for the people who are stuck thinking "I don't know what to build" or are overwhelmed by having to design the app and the features and the UX and simultaneously learn a new framework (React/Angular/anything really), it can be helpful to isolate just the "React" part of that learning experience by copying something that already exists. It reduces cognitive load, and focuses the expended energy on one specific learnable thing.

It's the difference between "build a social network app" and "build Twitter." The former could be anything. There are a ton of decisions rolled up in "a social network app."

I guess an analogy might be, learning woodworking by building a tried-and-true beginner project vs. learning woodworking by building a custom-designed archway. Sure, you'll learn a ton with that archway, but maybe start with the easier thing, to learn the tools and learn how to measure and cut. Then go build the archway.