I disagree. The cave is a mere decoration, which serves nothing other than esthetic. Deep substrate acts as a insulator against water loss. Its one of the reasons burrowing desert species dig down and stay down. They are conserving their water by retreating to cooler, damp levels. A glass cage really isn't proper reptile container, while a custom cage built to the reptiles needs would be best. If I was keeping Uros, beardies, or savannah monitors I would build a solid, water proofed base, with 150F basking area, cool side ambients no lower than 78F. Substrate would be damp sandy dirt (a foot or more deep) to allow deep digging and tunneling (its what Uros are built for). Minimal ventilation, in fact, zero vents at top of cage, and feed it daily. Its the difference between a lizard living a few months to a life measured in years.
About burns: if the cage is sub proper in temperature, the lizard will bask incessantly to stay within levels for digestion, or to meet daily internal needs. Your lizard should bask no more than a few minutes at a time, not lay under it for hours. Thats where burns occur. Little has to do with the high basking temps, instead its all about the ambient meeting the lizards needs.
Do some basic searches for your lizards natural habitat and temperatures and you'll see what I am trying to explain. Good luck, John
what humidity does an uro needs?