The impossibility proof actually stands if you require only one processor to decide (this is mentioned explicitly in the paper). So X out of N is just as hard a

The impossibility proof actually stands if you require only one processor to decide (this is mentioned explicitly in the paper). So X out of N is just as hard as N out of N. Some methods for ensuring a total ordering on message delivery require a round of consensus. Google's chubby lock service requires five servers out of five to achieve consensus. Database commit requires (at least) majority consensus if you're using quorums. You're right to argue that practically this result doesn't really affect anything in the sense that you can fake synchrony with sufficiently large timeouts, but at the same time systems that are using hard core distributed algorithms such as Paxos are highly critical and it makes a lot of sense to be aware of what is possible and what is not.