I've been out of the React Native loop, but I seem to remember Nuclide was FB's canonical IDE for React Native and Hack - does that mean there's not an official way of using those environments any more?
In the past, a new platform required a new language which required a new IDE. Fortunately those days things less tied together. React Native is mostly using JavaScript which can be productively edited with a lot of editors and IDEs.
So the fact that Nuclide was there didn't mean that you had to use it (and the vast majority didn't) in order to write React Native.
I find this a little disingenuous, since React and React Native documentation rarely if ever feature code examples in any actual flavor of standard JavaScript and the 'blessed' way of writing React app involves quite a bit of embedded XML (JSX), which editors need to know how to deal with.
So the fact that Nuclide was there didn't mean that you had to use it (and the vast majority didn't) in order to write React Native.