Re: Very poor by design.
I think you're assuming much more thought went into it than actually did. More probably something more like this :
Select page_text where language_id = device_language_id
So, nothing returned when a device language hasn't been included.
I know this thing got written in a rush, but a decent developer would have spotted that using a default was necessary when doing this for unsupported languages. Which is worrying, as an app of rather some importance in a serious crisis shouldn't be written by inexperienced junior coders.