The only reason I used Time was the return to hand aspect. Seemed to fit best in Time. But, you are right, thematically Fire would probably be better. But, if you saw the latest Clash of the Titans movie, teh Djinn were rock like creatures that wandered the desert. And desert fits with Time to a T. So, that's how I envision them more similar to the CotT DJinns and less so to the Muslim ones.