It depends. From the link:

> If, for any reason, developers need persistent storage [...] they can do so by using the navigator.storage.persist() method of the Storage API.

This makes a request for guaranteed permanent storage ... which can be approved (or denied) by the user or by browser defaults.

Edge case but playing devil’s advocate: a user can also uninstall the native app at any time, and might still expect their last change before they closed the app to be reflected in the web version.

You can never truly trust anything about a client because by definition you don’t control it