At first installation, this windows has default value and the language zone too. It tries to find the OS language and matches the best one in this list to the OS language.
If nothing is found, then English is the default.
Did you change another setting in this windows and hit OK whithout looking at the default value in this zone ?
No - I don't think so.
So...I deleted the registry entry for APG 3.0 and then ran the program again.
The UI is in English but the Language setting is 'German' - see screenshot.