I usually try not to assume that because I don't understand how something works that it doesn't. This is how I think it works for me. My apartment is kept around 75 (bit warmer than 71), I set my on/off thermostat to 78 in the location described above. The RHP kicks on and heats the objects below until enough heat is cast off to turn off the tstat. Sometimes the probe directly under, on top of the substrate reads up to 100 or so but it does not stay that temperature if something comes between it, my hand or a snake. The snake can go to the warm end at say 82 degrees with the RHP on and soak up enough energy to warm up to 84 (for example) and then move away when it wants to. One of my snakes prefers to stay in the hide on the warm side after it has eaten and I measure the temps in there at around 85 or so usually. I think the on/off tstat also helps prevent overheating in the case that a snake does not move to thermoregulate, but if that is the case there may be other problems with the animal as well.
This is just my limited understanding of how it works and observation of how it has worked well for me. For a detailed conversation about it I would call Bob at Pro-Products because he seems to enjoy discussing the dynamics of heat in detail. Cheers.