As I said, that use case was out of the window long before. From the start, as far as I know.
No browser has ever given you any definite promise on whether your local storage data will be kept. That's also true for IndexedDB. So you need a mechanism to restore that data, be it cloud storage or something else.
If you wanted to support Safari private browsing, you even had to deal with local storage not being available _at all_.