It turns out that the cordova barcode scanner plugin supports different sets of barcode formats, depending on the host platform.
Specifically, android vs iOS:
Android:
iOS:
The project I've inherited: meant to read CODABAR labels on Android and iOS...
It seems this difference in formats stems from the way the android version uses the official java ZXing library.
The iOS version uses an ancient C++ port of ZXing, which didn't yet include these formats.