I mean it literally. It might be not yet even assembled at a factory, not delivered to its destination country and not sold to a user.

Ah, well that doesn't really matter, you can still see them as two separate participants in an asynchronous protocol.

End to wnd encryption is when on one end you encrypt data for every remote end that is supposed to decrypt this data. That's why it is called end-to-end, because all ends are known and nobody can tamper the correctly established communication with correctly verified recipient. That's how all e2ee protocols work, otr, omemo/signal, etc.

If you do not know what end is going to decrypt it, is is just an encryption with a key/password. Anybody who has the credentials can access the data.

These WhatsApp backups could be restored by 50 different 'ends', so using e2e in this context is incorrect.

Yeah sure, you're saying that the model for full disk encryption would be more relevant here. But at the same time, there is a third-party server in the middle of the protocol, and so I'm not sure if that model would be more relevant.