In Nutanix you can’t go from a 3 node cluster to a 2 node cluster but of course you can repair and replace the failed node in a 3 node cluster, without downtime.
If you had a 4 node-cluster you could remove the failed node and continue running the cluster with full functionality as a 3-node cluster.
That is what the document on the Nutanix portal is about.
What important is that in case of a node-failure in a Nutanix 3-node cluster, the data will be rebuilt and once rebuilt the cluster can sustain additional disk-failures without downtime/dataloss and node-failure without dataloss.
Disclaimer: Nutanix employee but try to stay objective.
// Linjo