Why can a linear power supply with PTC short-circuit and pass the current point

Under normal circumstances, the linear power supply is not allowed to short circuit and test the overcurrent point, but when the linear power supply is added to the "PTC thermistor" component, you can do short circuit and overcurrent testing. Because the PTC thermistor in addition to being used as a heating element, it can also play the role of a switch, the current through the element causes the temperature to rise, that is, the temperature after heating rises, when the Curie point temperature is exceeded, the resistance increases, thereby limiting the increase of current, so the current drop leads to a decrease in the temperature of the element, the decrease in the resistance value also increases the circuit current, and the temperature of the element rises. It is repeated, so it has the function of keeping the temperature in a specific range and plays a switch role. Using this temperature resistance characteristic can play a role in protecting the power supply from overheating.