Why the locale ko-KR uses dayFormat 'Do' as other locales don't?

[jinhyeok15]

I found the issue when I updated antd v5.8.0 to v5.16.0.
I saw v5.14.0 support that DatePicker all date-related information in the panel will allow configuration through locale.
The reason that dayFormat in rc-picker is configured as 'Do', when I set ConfigProvider locale prop option on koKR, UI changes like below.

Before

After