the whole premise (that i m sold on react-native) is that it lets you use code from your react app and run it natively.
And the concept of cross-platform is not only for "similar" platforms like mobile, but across disparate platforms, like mobile AND PC. Otherwise, what's the point of cross-platform?
As I said, that's not what people mean when they talk about "cross platform" in this context. Go to phonegap and see if they support PC. Cross platform means you should write once and it works everywhere without modifying anything, just like the web. But you can't be cross platform AND native on completely different types of platforms, since each has its own distinct feature sets. You are free to believe whatever you want but that doesn't really mean anything since you're basically arguing about something that I'm not even talking about.
