You're correct. The rules are very loose for dead rubbers; in fact, there really aren't any rules. They can play best of three, substitute players after the deadline, and even agree to cancel the matches. Technically, they're supposed to take dead rubbers seriously, in case somebody tests negative down the line, but in practice, as long as the supervisor agrees, they don't go by the rules for live rubbers.
Edit: Actually, IIRC, best of three dead rubbers is now the norm; it's the cancellation that the supervisor has to approve.
Are you sure?
Can you present me an example of a tie where more than 4 players represented a country?