The MG EU description of TJA is correct. I know it steers as I have first-hand experience of it.Agreed. ACC does not steer, and neither does TJA as far as I can see from the MG UK information.
Should also be noted that in the Mk1 5 and ZS that TJA does not exist in the menus.
As pointed to in the above link as described by MG UK
1. Adaptive Cruise ControlAdaptive Cruise Control uses smart technology to detect what’s in front of you. It will then change your speed depending on the current situation. For example, if the roads are clear then you are set on a steady course, but if a car in front begins to slow down, then it will use the brakes to gently reduce speed. This helps to prevent any collisions.
4. Traffic Jam AssistWith our Traffic Jam Assist technology your vehicle can come to a stop and then accelerate again by itself when it detects a traffic jam. It does this by monitoring the car in front and automatically following its pattern.
6. Lane Keep Assist (LKA)Lane Keep Assist (LKA) goes one step further than the Lane Departure Warning and actually corrects the driver’s position for them. By taking control of the wheel it adjusts the vehicle’s position to keep it within the lane markings.
However MG Europe describe it slightly differently MG Pilot safety features: how do they work?
Traffic Jam Assistance (TJA)When Adaptive Cruise Control is turned on, Traffic Jam Assist continuously monitors the speed of the vehicle in the front. If the system detects dense traffic or a traffic jam at speeds below 60 km/h, the driver can activate TJA. The driver’s vehicle will automatically follow the vehicle in front, controlling its acceleration, braking and steering within the same lane.