wifi calling will enable HD voice quality on calls. Have you done FaceTime audio? If you have you will know what a difference it makes. No more of those static noise in the background. Also wifi calling enables you to make phones call back to the US for free when you are out of the states.
I'm still not understanding it. Will the HD quality on a wifi call sound better than calling over Tmobiles network, or voice over LTE? Even disregarding that, I use google voice for every single phone call I make in or out on my cell phone and it sounds great.
Not trying to be a troll here, but I just am not understanding what the big deal is or where they are forging new ground.