suppressAuth is not related to the dataset read/write settings, but instead to the CMS collection’s read and write permissions. It does not alter any pre-set settings.
In the code, if suppressAuth isn’t used, the code might throw up an error if the collection settings are set to Admin. So I’ve just added that extra bit to make sure that the item successfully gets deleted even if the permission to update the content is set to Admin. If you want to exclude suppressAuth, you can simply change your collection settings to Anyone, but that may expose your collection and make it vulnerable, hence suppressAuth. (: