Thanks for highlighting the issue. I also faced the same, but in my case, the iOS implementation was missing.

ReactNativeBlobUtil.config({
        fileCache: true,
        title: '##### Recipt',
        addAndroidDownloads: {
          useDownloadManager: true,
          notification: true,
          description: 'Downloading file...',
          mime: 'application/pdf',
          path: path
        },
        path:path,          // <----- missing
        appendExt: "pdf",   // <----- missing
        IOSBackgroundTask: true,
      })