In my experience, state management hasn't really been a bottleneck in iOS development, at least not to the point where it could account for half the effort of a project (or even 25%), and I've worked on some monster iOS apps.
Forgive me for being skeptical here, but I think this is one of those extraordinary claims requires extraordinary evidence situations. "It works great" sounds great and all, but I'd have a hard time convincing a dev team to adopt an approach because someone says it works great :)