Brett Meyer commented on an issue
Hibernate ORM / Bug HHH-7390
@ElementCollection annotated properties do not generate a correct PostUpdateEvent
Here is the use case :

an @Entity has a property annotated with @ElementCollection.
Let's say we registered a PostUpdateEventListener in the SessionFactory

If we update this @Entity, we end up with a PostUpdateEvent whose oldState value is equal to the state value whatever the loadedState of the EntityEntry.