This attribute comes in clutch for pages that serve as the default Variation for buyers whose language or locale doesn’t match any hreflang tags.  It will even allow you to incorporate the default "x-default" tag for customers from nations around the world for which the language is not configured on https://addons.prestashop.com/en/seo-natural-search-engine-optimization/31857-automatic-google-rich-snippets-json-ld-open-graph-seo.html