Their flesh isn't significantly different from ours--if it would burn you, if you sat on it for 3 hours, then it will burn them.
But burns aren't the only issue--internal temperatures are as well. A ball python cannot handle having an internal body temperature much higher than 95F for any significant period of time--their health will suffer, even if they aren't burned.
Having a 95F hot side temperature, with a normal 80F cool side, however, is not an issue. The snake can move to the cooler area when its body temperature gets too high.