See the FIXME in MwTimeIsoFormatter::getMessage
|Open||None||T87764 Bugs related to time datatype (tracking)|
|Resolved||hoo||T104447 MwTimeIsoFormatter forces time precisions to be displayed in English|
The problem is being reported in regard to centuries specifically; see [[:d:WD:Contact the development team#Century dating—localization]]. (This does not mean there aren't issues with other dates as well.)
Evidently not (see Nikki above). But then aside from the translation issues, the "English" is just simply wrong, because in English (British, American, or otherwise), you'd never say "12. century." You'd say "12th century."