I think this is a misrepresentation of what makes React.js valuable. React is useful for optimizing your rendering (model state -> DOM state) because you don't have to think about re-rendering sub-views of things that haven't changed. This has nothing to do with defining a communication flow for your app. You're still propagating state up and down your tree whether it is a tree of Backbone views or React components.

Rendering optimization is definitely a nice thing to not have to think about though.