This is no longer creating a full package since packages are NuGet only since v9. You can still export these items and make them part of your package, that's why this is exporting a zip file with all the XML definitions in it.
Read more here: https://docs.umbraco.com/umbraco-cms/extending/packages/creating-a-package
And if you're creating a package I would highly recommend starting with the Opinionated Package Starter: https://github.com/LottePitcher/opinionated-package-starter - this will help you more easily fill in things like authors and readme and such.