You should consider rereading Leslie Lamport's original paper. BFT is a property of corrupt votes, not the network. You keep trying to make it about the network. Like, if you want to have a conversation about how the network can influence the system's fault tolerance, you should instead consider the network topology -- as in, which routes between honest nodes include corrupt nodes. This is also considered by the paper, since corrupt nodes can censor or rewrite messages, and thus influence how many corrupt nodes the system can truly tolerate, given a network topology. But in no case does message delay give a BFT system's node an excuse to make forward progress without first verifying that at least 2f+1 replicas agree with its decision. Even voting on a view change to remove a presumed dead node requires a 2f+1 vote.