I have leaned more since posting that.
The evaporation of the water in the water bowls creates a cooling effect. So in a heated room (or not) the snake can thermoregulate by bowl hugging. Well, I knew evaporation cooled but didn’t connect it to this topic until now.
However… On the main point. for ball pythons in the temperate temperature UK or USA equivalent, it would be expensive to heat my whole snake room to tropical Africa temperatures.