I don't see this as sufficient reason not to join a platform like Fabric. This could make it visible to a lot of developers who don't even know about deep linking, or that it can be done with an SDK. A big appeal of Fabric is also how easy it makes it to integrate kits into apps. You may be experienced enough to do the plumbing yourself, but the convenience Fabric brings lowers the bar to entry for many.
No relation or similarity to React; this isn't a UI toolkit but a platform SDK.
Fabric is the rebranding of Crashlytics, a crash-reporting SDK, combined with the Twitter ecosystem SDKs, and their ad platform, and so on. It's a "Twitter Inside" SDK.
To quote an earlier comment of mine:
"a souped-up Twitter SDK + Crashlytics + their bundled ad platform MoPub. The idea is you'll develop your app with this SDK and get crash reporting, usage stats, ad serving, 'Sign in via Twitter', Twitter integration, and [a bunch of] other stuff for free."
