Well same thing about VoLTE. I already created a thread about this problem two weeks ago, where I described it in detail, but nobody responded.
https://discuss.grapheneos.org/d/7872-gos-blocks-the-ability-to-enable-volte-tho-the-device-and-my-carrier-support-it
Seems like its not a big problem for them... That doesnt mean that I'm from Spain tho, its obvious that these features (VoLTE and VoWIFI) are limited for specific carriers, again whats the point if the device supports it and GrapheneOS is used by people all over the world.
That's why I wrote in my post "It would be very useful to not restrict this so that everyone whos using GrapheneOS with different carriers around the world can have the ability to freely enable and use this feature." Because it doesn't just affect only me.