To be clear, this paper is referring to non-decentralized (highly-consistent I assume) consensus algorithms where the goal is to operate a cluster of machines a

To be clear, this paper is referring to non-decentralized (highly-consistent I assume) consensus algorithms where the goal is to operate a cluster of machines as one logical system. You use this, for instance, to maintain high uptime in the face of individual machines going down. I suspect you were reacting to decentralized consensus (blockchains) which is a pretty different space.