An SEOer that has some experience with TLDs and language folders told me the following:
If you use language folders in site (like example.com/en/, for all English pages), I should also give hreflang en to all pages in that URL folder - but only if these pages are created as translations.
Is it true? Shouldn't it be given also to non-translation webpages in that folder?
hreflang may be used on any link. It doesn’t matter from which and to which document you link. It just conveys in which language the linked document is.¹
hreflang+alternate may be used only on links which point to a translation for the linking document.²
¹ In practice I’d only specify the hreflang attribute if the language of the linked document is different from the language of the linked document. For example, it makes sense to use it if your page is in German and you link to a Stack Overflow question (= English).
² Unless the linking document’s html element has a lang attribute with the same value like the link‘s hreflang attribute. In that case it wouldn’t be considered a translation, understandably.
