Depending on the country you made your Apple ID in that will be default interface language ,
however if you change your interface and region ,it may change ,although when your Log in ID times out it will go back
to default . I want to Apple to Bi lingual user interface we can choose any 2 languages on any platform ,because many users are not native English but many are bi and multi lingual .
Japanese Key board is Haragana and Romaji =roman
Even Japanese do not use Hiragana =Kana preferences on Qotoeri
They type using Roman then it is converted to Kanji , I use Hiragana,but the drop down menu of many kanji makes it difficult to render the correct reading as many kanji have many readings
All this technology and time and workers and we can not even get a decent multi lingual
Interface , All the code writers have to do is to design a field that can contract and expand depending on the localisation
Text and insert any 2 languages
We can not even customize localisation on OS 7 8 9