Just theorycrafting here, not saying I have an app that fits the description.
Wouldn't you want client side statefulness if you have an app like an online spreadsheet (google sheets, microsoft excel) that could occasionally lose connection but you still want users to be able to continue working on their document?
Yeah offline or complex client side state management is a good use case for Javascript. There are Hooks and Push Events with Liveview for real time integrations with Liveview in those scenarios. In my experience offline requirements are rare and often in mobile scenarios where a native or Flutter-like approach is a good option.
And no, your app is not that 0.000000000001%