I am new to these forums but I am not new to snakes. I have garter snakes growing up, a red tail boa, and a kingsnake back in the day. With my red tail, I learned about the "belly heat" idea... but when setting up my enclosure for my new baby ball, my girlfriend and I decided to forgo the uth and stick with bulbs for the heat. My thought is, heat does not radiate from the ground in the wild, it comes from the sun which warms everything else up. So, I am going to go with that for now.
Either way works, but your ball python is nocturnal. Which means, the sun warms the ground, and then the ground warms your BP when it comes out at night. So, actually, heat does radiate from the ground in the wild.