I am still encountering this on latwst GrapheneOS. I have tried Graphene's mesaging app, Google Messages, amd Fossify Messages. None of then are able to swnd premium sms to short-code numbers, because none of them are able to request the Premium SMS permission from the system. Under Settings > Apps > Special app access > Premium SMS, it simply says "No installed apps have requested Premium SMS."
This is clearly a bug, because normally sms apps do request that permission when needed. The fact that the apps don't even show up on that setting page as options to enable means that something is wrong with the Android system's handling od this permission.
Does anyone else acknowledge this problem?? Does it not affect most users somehow?