While writing a unit test for 5.3.6, I was unable to reproduce the bug. The reason is AbstractEntityPersister line 3270. In 5.1.0, it doesn't compare the jdbcBatchSizeToUse, and useBatch is true. This leads to lines 3291-3294 being executed. In 5.3.6, it only uses a batch when jdbcBatchSizeToUse > 1, but then BatchBuilder lines 69-71 never actually use a NonBatchingBatch.

Unless a new class is written in the future, which extends AbstractEntityPersister, and overrides the update method, I don't see BatchBuilder ever returning a NonBatchingBatch.