Apple controlled the choice of hardware in the iPhone and could easily have picked a modem that came with AMR-WB codec support. It's not as if the codec has one

Apple controlled the choice of hardware in the iPhone and could easily have picked a modem that came with AMR-WB codec support. It's not as if the codec has onerous hardware requirements. Yes, putting it in the original iPhone would probably have been a feature too far, but it could have been added to any iPhone from the 3G onwards as I understand things. It's exactly the kind of premium feature that you'd think Apple would have loved to have had associated with the iPhone. Whether they could force the operators to upgrade their networks is another question though.