NSBatchDeleteRequest does not delete external files

When using batch delete to delete a core data object, the object's external binary data is not deleted. Am I doing something wrong? Or is this a bug on Apple's end?

To reproduce:

-------------

I've set up a simple Core Data project. The data model defines an `ImageProperty` entity with a binary data attribute that "Allows External Storage".

I don't make any changes to the implementation of the persistentContainer that is provided by Apple:

lazy var persistentContainer: NSPersistentContainer = {
     let container = NSPersistentContainer(name: "ExternalStorage")
    container.loadPersistentStores(completionHandler: { (storeDescription, error) in
        ...
    })
    return container
}()

On application launch, I create and save an instance of `ImageProperty` with data large enough to be stored externally. I then immediately delete that property using a batch delete:

let entityName = String(describing: ImageProperty.self)

// Create property

let entity = NSEntityDescription.entity(forEntityName: entityName, in: persistentContainer.viewContext)!
let property = ImageProperty(entity: entity, insertInto: persistentContainer.viewContext)
property.data = NSData(contentsOfFile: Bundle.main.path(forResource: "sample-house-a", ofType: "jpg")!)
try! persistentContainer.viewContext.save()

// Batch-delete property

let fetch: NSFetchRequest<NSFetchRequestResult> = NSFetchRequest(entityName: entityName)
let request = NSBatchDeleteRequest(fetchRequest: fetch)
_ = try! self.persistentContainer.viewContext.execute(request) as! NSBatchDeleteResult
try! self.persistentContainer.viewContext.save()

When I check the app's sandbox, the item has been deleted from the database, but the external file still exists. Why?