That still seems like a poor design. This would also happen if you cleared localStorage before the data is synced. If, for example, when you came back online

That still seems like a poor design. This would also happen if you cleared localStorage before the data is synced. If, for example, when you came back online and were trying to do something on an unrelated site, hit a bug and tech support asked you to clear your browser. For something as critical as financial records or vaccine records, the sensible thing might be to not work in offline mode, or to persist to native storage. I think it's fine as a cache for offline data for a lot of use cases (i.e. task trackers, note apps, shopping lists, etc). But it creates an unacceptable risk for business critical data, imo.