i'm guessing it has to do something with the adrenaline going through your body. Of course there is windchill falling at 120 mph. But if the temperature decreases as you climb to higher altitude, then it must rise as you fall to lower altitude. I'm guessing that maybe along with the adrenaline that your body is warming up because you are going to lower altitude (yes even with the wind chill) and maybe you dont notice it because the temp is rising.
I personally dont feel the temp. in freefall but as soon as I am under canopy my hands are FROZEN!