As my answer on the other question you referenced shows, typical in slow cookers, "high" and "low" do not refer to temperature -- they do not contain a thermostat. Rather, "high" and "low" refer to the power of the heating elements.
(If you need a refresher on the difference between "temperature", "heat" and "power", now's a good time to go to your high school text books).
The heating elements are on constantly, one for "warm", another for "low", both for "high" (on cheaper models). The ceramic pot spreads the heat so that the food doesn't burn. Some of the heat is lost through the walls. Some of the heat raises the temperature of the contents. If some of the liquid content reaches a temperature where it evaporates, then that's what happens, and the heat is used up that way instead.
The slow cooker has no way of knowing what temperature your food is at, or whether it's boiling. It just keeps pumping out heat. However, typicvally the designers have picked suitable powers such that:
- "high" will bring a full pot of cold-ish contents to boiling point in 20 minutes or so, but it's not powerful enough to power a full rolling boil.
- You can turn it on, do something else for "a while", then come back to turn it down to low.
- It will never boil over, but if left for a long time it could conceivable boil dry.
- "low" will bring take an hour or more to bring a full pot of cold-ish contents to boiling point. Once at that point, it will fuel a very gentle simmer indeed.
- This means it takes a long time to cook, because for a good chunk of the first hour, it's not hot enough to be cooking.
- You can leave it all day long, with no fear of it boiling dry.
- "warm" puts approximately as much heat as the designers expect to be lost out of the pot walls, so the temperature stays approximately constant.
Some models have an "auto" setting, which is effectively a timer which switches from "high" to "low" after a period - so it gets to boiling point quickly, then stays there all day.
All of this is very approximate: they are not manufactured to strict tolerances. The ambient temperature in your kitchen will affect performance -- in a cold kitchen it will take longer to reach boiling point and simmer more gently; in a warm kitchen it will boil sooner and more vigorously. Atmospheric pressure will affect the boiling point of your food.
I learned this the hard way. I thought I could be greener by wrapping the slow cooker in a towel, so less heat would be lost out of the side, and the thermostat would cut off the heaters sooner. Since there is no thermostat, however, all that happened is that the food boiled too hard.
So, recipes don't give a temperature range, because slow cookers are not set to a temperature. The temperature is "the boiling point of the contents". The recipes can work with the variety in power between different models, because they are recipes with very broad tolerances.
Good slow cooker recipes work within all of this. They are not particularly sensitive to temperature or time. For example, a stew made with a cut of meat that responds to slow, gentle cooking. A lamb shank might be done after six hours in a slow cooker - but another two or three hours won't hurt it. The classic slow-cooking scenario is that you start a meal cooking in the morning, not knowing exactly when you'll get home to eat it. So if you seek precision, slow cooking probably isn't for you.
However, there's certainly a good geeky project for someone who wants to build a slow cooker that's truly frugal with energy: add a thermostat, add plenty of insulation, have it bring the contents to (say) 100°C then keep it there with the thermostat. On the other hand, you can get similar results by simply bringing a stew to the boil then transferring the pot to an insulated box.