If the network is allowed to drop packets there are times where either you must not respond to requests (as doing so would violate sequential consistency) or you must respond incorrectly, potentially with stale information.
The network partition that forces you to drop one of these guarantees might be quite dramatic - but note that, for example, a quorum system is only available on the majority side of its partition. Therefore if a single node is unable to deliver messages (due to a network partition event), it will not be able to correctly respond to requests and must either not respond to its clients or respond incorrectly.
So then what am I missing? It sounds to me like the rest of your post is reiterating what you just called incorrect.