Why does Excel display a built-in date format differently according to OS region setting?

According to https://support.office.com/en-us/article/Format-a-date-the-way-you-want-8e10019e-d5d8-47a1-ba95-db95123d273e?ui=en-US&rs=en-US&ad=US&fromAR=1, the built-in formats starting with an asterisk (*) are regional. They will display different format according to your OS region.

I specify a custom format dd/mm/yyyy hh:mm in a cell, the first weird thing is, Excel treats it as a built-in format, id is 22. According to ISO/IEC 29500-1, Information technology — Document description and processing languages — Office Open XML File Formats — Part 1: Fundamentals and Markup Language Reference, 18.8.30 numFmt (Number Format). ID 22 is m/d/yy h:mm

The 2nd weird thing is, the built-in format which is not regional, also display different format upon different regions.

The only explanation I found is in 18.8.30 numFmt (Number Format),

... Some of these Ids can be interpreted differently, depending on the UI language of the implementing application.

Does anyone know the reason of this behavior?

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