Pinging is a form of gossiping that only happens when a node is neither a master, nor following another master. The setting
discovery.zen.master_election.ignore_non_master_pings determines whether a node only takes information from master-eligible nodes into account when deciding to join an existing master or trying to become master. Having it set to true allows a data join to rejoin a master that it only learned about from another data node, but which it did not directly got information from. It does not have any influence though on which node is pinging which other node, so I'm not sure how it could relieve some pressure from the masters in a large/busy cluster.