Is byzantine fault tolerance a really necessary for a crypto? I consider stellar to be one of the "sane coins", in that the protocol seems to make sense for what it is trying to accomplish... for the most part.

I dug into stellars protocol about 3 years ago, so my memory may not be all that fresh..

Anyway, it's seems to me like for a digital currency, where each token has a different "pedigree" if you will, it's not necessary for everyone to agree on the complete state of the network, but only have enough information for ordering actions on a specific wallet.

So when you are spending or receiving, you don't care about the state of everything, but just one wallet, and if you are accepting, you just need to refute the existence of a new transaction on that wallet.

Hopefully you understand what I am asking: Do nodes really need to agree on everything, or simply have enough information, so that a recipient can query enough nodes to avoid a double spend situation?

PS I've also been looking at nano more recently, as it resembles some ideas I had myself, that both senders and recipients should sign transactions.