But there are different levels of state: completed transactions (application finished and submitted), partial business logic transactions (three out of five steps completed) and "app state" (field 6 of form 4 partially filled in etc).

They can all be kept diffently in sync (in sync, because the browser will keep partial state via native widgets if nothing else). Even w3m keeps track of inputs in forms before submission.

As I mentioned, I think complex business flows like these can be a great reason to go from "web page" to "web app" - precisely because it enables rich, ephemeral client state with (some) business rules close to the client.

But that doesn't mean you can't do powerful things with just html/http and some form of continuations etc on the back-end.