Spacey I have had the same frustrations under different circumstances. I think the reason that they don't put exact numbers on their thermostats is because if they did then they would need to actually make the device go to that temp and they know that since the thermostats are so cheaply made with such a large swing between them it is impossible. They would have warranty returns all the time.
So they make it simple by making a thing that gets hot in the middle and hotter turned all the way up. I noticed the same trend in car gauges awhile back. No real nunbers ,you just know you have oil pressure. You might know the water temp is getting hot but never know exacly how hot it got.
A lot of the things they sell for kitchens are like that. My stove has poor control as I have one of those electric stoves with the burners under a glass top. They constanly run away on temps either too hot or too cold. The best control is a gas range. All the top chefs use gas.
I just bought one of those George Forman grills with the removable heat plates. It does have a more exact thermostat on it but I haven't checked to see how accurate it is.