It seems like changing it in that menu does nothing - however, whether it is enabled or disabled by default may matter. Hellraised I9100 firmwares seem to almost always provide better battery performance with the UCKH7 modem than I777 firmwares, and FD might be part of the reason why.
UCKK6 modem had power consumption issues for me. Drain at my desk (weak signal) was higher for the UCKK6 modem than UCKH7 running on a device with a permanent wakelock held! (A bit under 1%/hour for UCKH7 normal operation, around 1.2%/hour for UCKH7 modem + wakelock and for UCKK6 + no wakelock) All of these are on XWKL1 system base running recent Daily Driver kernel releases.