Exactly, Google will never add codes to Android KitKat that tells T-Mobile about unauthorized Tehtering.
/sarc
/sarc
I put a SIM connected to one of T-Mobile's $30/5GB prepaid accounts in my iPhone 5. When I try to turn the tethering function on, I get a prompt telling me to go to a T-Mobile website to get on a plan that supports tethering.
The carrier control of tethering made sense back before the iPhone had market dominance. Now it's stupid and user-hostile.