I'm not seeing any of this on T-mobile cellualar or otherwise. This leads me to think it is either something enforced by the USA inside the USA, or something only allowed in the USA. (I'm in the EU to be specific)
You tried sending and receiving links to those exact sites over SMS, and the messages all came through? I ask because multiple other people in this thread accidentally tried just accessing those sites over T-Mobile's cellular data, which isn't what's blocked.