Nor does Y-bar's example from EUR-Lex, where the language list is below the catalogue information. It being right at the top in a banner of hyperlinks with 2-letter codes is not actually a part of the pattern. The E.U. Parliament and E.U. Court of Justice use drop-down menus with the full language names, for example.
* https://www.europarl.europa.eu/about-parliament/en/parliamen...
* https://www.europarl.europa.eu/about-parliament/cs/parliamen...
The headlined page, as was pointed out, is just some system administrator's own WWW site, moreover.