Agreed. Also CTEK has no idea on the user’s car make and model, whether it has a current sensor or not or if the car is equipped with i-Stop or not etc.
But also per RichardFX comments, charging via the current sensor does pose a risk to confusing the car’s BMS, especially if the external charger is poorly designed and say overheats the battery giving the sensor an overly high temperature reading if you tried starting the engine soon after removing the external charger.