The IndexMode.PRIMARY_OWNER strategy is suitable for single indexes cluster-wide, that happens when using InfinispanIndexManager and ElasticSearchIndexManager. On this case, an entry should be indexed only once since all new joining nodes will see the global index.

For the cases where the index is local to each node (near-real-time and file system index managers), the state transfer data should definitely be indexed, otherwise when ownership of a key changes the entry will be kept in the 'old' owner.