I don't understand the goal of 0% platform specific code (on a lower power device where UX is very important) or even further being able to make a whole app without having to learn about the platform, being aware of its conventions and limitations.

I've never finished a React Native app without native code. I've done a few now and I've come to believe it's not worth even trying to avoid it and sometimes worthwhile to look for places where a little native module can yield performance or UI wins. React Native is the glue or orchestration and it is, to me, extremely good glue.

I haven't seen many people beyond the tutorial level suggest otherwise. It provides a common structure (which is enormously useful), and some quick consistency wins for simple stuff like your About Us screen.