I am following the convention from many other places. I can guess the could be to have the manifest as small as possible and to truncate the non-required fields in the manifest. 

You can see the same convention was followed here - https://github.com/animoto/animoto_api_client_java/blob/b4c27b5072c7396865234e61ab37c921d564c6ca/src/main/java/com/animoto/api/ApiClient.java#L518-L524