While I'm not advocating their use, I'd love to "hear" from one person who has burned a reptile with one or at least shot the temp of one.
When I was a very little girl I had an Eastern Hognose. The internet isn't what it is today (I'm young enough that it existed, but just barely) and there weren't many resources available about proper husbandry. We kept the snake in a 10 or 20 gallon (don't remember which) with a heat rock. Usually we were able to turn the rock off every night, but one night my mother got very ill while we were at her friend's home and we couldn't get back to turn off the rock for two or three days.

We came home to a cooked snake, curled up basically fried on the rock.

We talked to the guy at the local small pet store and he told us that he'd heard of that happening before, but not often. I was only five years old and was so upset about my dead snake that I didn't talk to my mother for over a month.

So from personal experience, I strongly recommend against ever using a heat rock for any species.