I think the important part of this discussion is that the finality of payments sit outside of the mechanics of the financial system. For instance - when a wire

I think the important part of this discussion is that the finality of payments sit outside of the mechanics of the financial system. For instance - when a wire transfer is "reversed" that is accomplished with another wire transfer (or some other series of administratively triggered actions). For both cryptocurrency and normal currency the system is a series of transactions that are treated as valid for a particular period of time. The decision to consider a transaction final or not exists outside of that accounting system. The fatal flaw of crypto currencies (edit: in this regard!) is they have comparably high fees built into the mechanics of their accounting systems. What a bank can do for "free" (really just very low cost) in fiat would compete for scarce transaction slots in crypto.