How does MongoDB process unsupported languages?

Question

I have documents that have a text field. The text could be one of dozens of languages, though most are supported by MongoDB (English, Russian, German, French, etc.). There is also a language field which tells MongoDB the language of the document's text field. How does MongoDB handle unsupported languages, like Urdu or Swahili? A post about MDB 2.4 suggests indexing cannot be performed on unsupported languages. An answer to this question suggests that indexing, but not lemmatization, is performed on unsupported languages. For my case, it is fine if no lemmatization is performed.