Oops, I should have clarified. Triggering sensor is easier when it is liquid. Using my hand to push raw sensor on ice or between two ice cubes was a pain. And it took a few minutes of waiting around.
Salt water is just easier to trigger the sensor. I dip it in water, and instant trigger. Ice was not as easy. Especially when threshold is lower than 32 degrees which is the case in quite a few BMS these days.
And never did I state that the salt would make it colder or change any other properties. I take salt water, put in freezer, take it out while it's a slushy/liquid state, stick in sensor. There was no other purpose other than time efficiency.