That's the reason that I said that LangStrings are pointless in his script because he isn't including the English language!
The script might only use English at the moment but perhaps there are plans to add more languages in the future? Adding the MUI_LANGUAGE line is an easier change than getting rid of all the language strings in the script.
Surely there is no harm in using language strings even if the script only uses one language, provided the necessary MUI_LANGUAGE line is used? Some of my installers start out as English-only and end up supporting several languages and I have found it easier to use language strings right from the start.