This attribute is available in clutch for pages that function the default Model for people whose language or location doesn’t match any hreflang tags.  It will even permit you to incorporate the default "x-default" tag for users from nations around the world for which the language will not be configured https://www.presta-addons-modules.com/en/seo/prestashop-seo-automatic-google-rich-snippets-json-ld-opengraph-twitter-tags-schemaorg.html