When we view the tile in quick settings it requests for SuperUser permission to perform its required work but when we close the quick tile panel it doesnt surrender(close the shell) SU permisssion .
To revoke permission i.e. close its shell we have to open the app and remove it from recents
When rebooting/powering off, iSu won't reactivate SU and will delete the /system/bin/SU and /system/xbin/SU files, requiring the user to reflash the binaries.