You're right. But as Lingua Libre support way more languages than wikibase do, so it is not possible to set the correct language in all cases. I see three solutions:
- hide with a small JS/CSS snippets the language (as a temporary fix)
- set the correct language if possible, and for unsupported languages use mul (multilingual) (need a bit of development, but it's not very clean in my opinion);
- change the datatype of this property from monolingual text to simple string, as the language is already explicitly defined in an other property (this is the one I prefer, but need to edit manually the DB).