In the application diagram of the datasheet, the current loop protector is placed after the sensor device and before the analog readout. This is because most of the time, the supply bus will drive more than one sensor. If we put the current loop protector before the sensors and the current drawn from the supply is greater than 30mA, the system will not work.
When users place the protector after the DC supply and before the sensor, in addition to protecting the reading device, this allows for protecting the DC supply in case the sensor input connection is shorted to GND. This configuration will work fine as long as the current required from DC supply is less than 30mA.