CC2530: CC2530 and cc2592 PA_LNA_PIN control

Part Number:CC2530

 dear all:

      door lock project :  CC2530 and cc2592,

      Some enddevice products are found continues to consume about 4mA of current,  

      The protocol stack that is currently used is  Z-Stack Home 1.2.0,  

      Contrast the latest protocol stack Z-Stack Home 1.2.2a,  function:  macRadioTurnOffPower() Increased     

      if (paLnaChip == PA_LNA_CC2591  ||  paLnaChip == PA_LNA_CC2590)
      {
        /* Set direction of P1_4 to output and pulled down to prevent any leakage
         * when used to drive PA LNA  */
        P1DIR |= BV(4);
        P1_4 = 0;
      }  

     My question:    why the forced PA_LNA_PIN  is 0?    Why does this PAEN_PIN do not require mandatory control？