City Safety assists the driver by continuously attempting to anticipate whether there are "escape routes" to the side in case a slow or stationary vehicle ahead is discovered at a late stage.
Your car (1) "sees" no options for evading the vehicle ahead (2) and can therefore auto-brake earlier.
City Safety does not intervene with the auto-brake function as long as the driver him/herself has the opportunity to avoid a collision via a steering manoeuvre.
However, if City Safety anticipates that an evasive manoeuvre is not possible due to traffic in an adjacent lane, the function can assist the driver by automatically starting to brake at an earlier stage.
City Safety's ability to anticipate a certain situation is an aid, and does not work in all driving situations or traffic, weather and road conditions.
The driver always bears ultimate responsibility for ensuring that the vehicle is driven safely and that applicable laws and road traffic regulations are followed.