Do you mean that, in order to keep ALL entity caches,
query.addSynchronizedQuerySpace("");
should be called? This trick is counter-intuitive, and is not mentioned in the doc.

Please also read
https://github.com/hibernate/hibernate-orm/blob/master/hibernate-core/src/main/java/org/hibernate/action/internal/BulkOperationCleanupAction.java#L148
Line 148 contradicts with the @return comment. This is another evidence of bug rather than by design.