UIDocumentPickerViewController - ignoring directoryURL - bug or programmer error?

The UIDocumentPickerViewController is not working, and I'm not sure if it's a bug or misinterpretation of the "documentation".

If I set UIDocumentPickerViewController's directoryURL, it seems to just ignore it.

For instance, directoryURL is file:///var/mobile/Containers/Data/Application/abcdefgh-abcd-efgh-ijkl-mnopqrstuvwx/Downloads/.

But this code opens it up in the directory from the last time I'd presented a UIDocumentPickerViewController:

Code Block   crosswordPuzzleDocumentPickerVC = UIDocumentPickerViewController(documentTypes: ["public.item"], in: .import)
    crosswordPuzzleDocumentPickerVC.delegate = self
    crosswordPuzzleDocumentPickerVC.modalPresentationStyle = .formSheet
    crosswordPuzzleDocumentPickerVC.directoryURL = crosswordPuzzleDownloadsURL
    fileBeingOpened = .crosswordPuzzleFile
    self.present(crosswordPuzzleDocumentPickerVC, animated: true)

Why isn't it heeding the directoryURL?
Any help would be appreciated, my app is this close to being ready to submit, but making the user scrounge for a folder just seems cheap.