i believe that tool is trying to use a temp root method to inject the su app and binary. even if the app manages to do so,an s on phone has write protections that will prevent those from remaining after a reboot,even with an unlocked bootloader.
from the description its not not doing anything to install a recovery,just attempting to add root access.
IMO,youre still better off manually adding a recovery and flashing the superuser files via the recovery. fact is phones are becoming too complex for universal one click methods to be of much use,and you may need the knowledge you get from the inital rooting process in order to fix minor issues that can arise from it.
again,just my 2 cents