I have done thermostat opening tests on the stove with a thermometer and a sauce pan full of water.
But I'm old enough that I can not recall if it started opening at rating or was fully open. That's why I went to a manufacturers website.
It is all good.
BTW... I was not trying to be antagonistic, I was just trying to find a source of info to clear the water so to speak. Sorry if I can off that way.