[tempfile]

The example they used for "in progress" state was form inputs. Don't you count those as in-page state?

[chii]

until you pressed enter, this progress is understood to be ephemeral. It has only been recently that the user has been 'conditioned' to expect the form inputs to be retained when they click a link, and it's because the app is trying to retain the state of ephemeral progress.

So you cannot have both a webpage that is not an app, but maintain an app-like behaviour. Trying to do so is a cursed problem, and it might succeed with high effort, but ultimately not worth it.