Pretty much, but the govt didn't do any blocking directly. They just told the carriers, "Hey, you must not allow people to use devices on your networks that are unable to make emergency calls, or we'll apply serious penalties."

The carriers then responded, "I notice that there is no requirement that we allow any device that can make emergency calls. So we will only allow devices we also sell (and maybe a few other models, if they're popular enough that we can't get away with not allowing them). And if that means more people than necessary will have to buy new phones, we will happily sell them new phones."