Upload asset documentation is incomplete

In the upload asset example at storyblok-file-upload-example/index.js at master · onefriendaday/storyblok-file-upload-example · GitHub, it is implied you can use these fields when creating the signed_url in order to upload the asset:
// add the id to update an existing asset. ‘id: 123,’
filename: ‘test.txt’,
size: ‘400x500’,
asset_folder_id: null

In actuality, it appears that one can set more fields when creating the signed_url:
id: imageId, // use to update existing asset
filename: filename,
asset_folder_id: folder ? folder : defaultAssetsFolder,
short_filename: filename, // listed in doc for asset object but seems to be ignored
copyright: copyright ? copyright : ‘’,
title: title ? title : ‘’,
alt: alt ? alt : ‘’,
ext_id: ext_id ? ext_id : null