However, in the html, there is a tag identifying the language as "ace" or Acehnese.
When you check the bar, there are options, one of them is to report an incorrect language detection. There is a drop down list of languages to select from with an option at the bottom to specify a language that is not in the list.
Adding this is best practice for a website but sadly many if not most websites get it wrong. It is intended to allow services like the Google translation service to know what language a text is in. The Localisation team will go a step further for MediaWiki; it will provide services based on the language indicated by this tag. Services like WebFonts, keyboard mappings and appropriate text direction settings.
Identifying a language is relevant, many services rely on it and it is what gives visibility to a language on the Internet.