I tried to understand how meta:Translations:Universal_Code_of_Conduct/2021_consultations/Announcement/1/ha-latn could be created whereas ha-latn is a wrong language code and T124013 has been fixed.
I just noted that Special:Translate?uselang=ABCDEFG automatically adds &language=abcdefg URL parameter and allows to create messages in Translations: namespace with /abcdefg language code.
Outcome
Special:Translate no longer allows making translations to unknown languages.