Why is the load current delayed from the voltage rise in PLZ series when the voltage is applied while PLZ series turns the load on?

PLZ series has the soft start function, which delays the rise time of the load current to prevent the followings;
– An unstable output from the DUT occurs due to a sharp load current rise.
– The overcurrent protection circuit of the DUT is activated.
The long set time of this function may have been chosen.
Set a shorter time of this function and check the load current rise time.