Would you try just
``` defaults read .GlobalPreferences AppleLanguages ```
to see what you get? Even with the same settings as yours, I get
``` ( "de-DE", "en-DE", "zh-Hant-TW" ) ```
and filtering this through the sed seems to do the right thing (Do you use the system `sed` or some other `sed`, e.g. from homebrew? What does `which sed` show?).