When running a bulk insert using the bulk API and an UNACKNOWLEDGED write concern the driver translates this into individual inserts, as opposed to an insert of the list.

Given the API user has indicated a bulk operation which is unacknowledged, it appears a single insert with all insert operations would be more appropriate. If the user wanted separate inserts, this option is available via the insert API.

For workloads where the number of inserts is high, the difference in performance is considerable