The reason it's kind of complicated is because when a node is shutdown or dies, it's published state does not get updated...so a down node could be listed as active. Because of this, the true state is a mix of /live_nodes and the state. If the node_name is listed under /live_nodes, then the state is the truth - if the node is not listed under /live_nodes, the state for the node could be anything and indicates nothing - the node is down and not part of the cluster.
This node is listed as active, but looking at /live_nodes:
It's 'node_name' is not listed, and so the node should be considered 'gone'. This is actually different than the 'down' state - a node might be listed in /live_nodes, meaning it's part of the cluster, but have a state of 'down' because it could not properly start.