The org.nuxeo.ecm.platform.audit.api.AuditLogger#logEvents log a bundle events. The AbstractAuditBackend as a default impl by calling logEvent for each item which generate an ES bulk indexing command per entry.
org.nuxeo.ecm.platform.audit.service.AbstractAuditBackend#logEvents must be refactor to use addLogEntries so it ends with a single ES bulk command.
Note that 8.3 is not affected because of the audit refactoring NXP-17934.