The probe issue still nags and nags - Most of the probes i've seen in the past have heaters but no temperature sensing
The probes I've seen (not a large number, but a few) don't appear to have any formal temperature senesing such as a thermocouple or thermistor in them. However, that doesn't mean they don't have a built-in temperature sensor. They do - the resistance wire heater element itself.
As you doubtless know, resistance wire has a positive temp coefficient, and has a higher resistance as it heats up. This within reason makes the heater elements self-regulating, as the current (and thus heat input) will decrease as the element heats up.
But a smart heater controller can measure the current flow and voltage to the heater, and thus determine the resistance. This, in turn, is a measurement of the temperature of the element. It isn't as sensitive as a thermocouple, but it can be pretty good -- especially since the main goals are to prevent the element burning out from overheat, while providing enough current to keep it above some specified temperature.
A better design would probably divide the heater element into 3 or 4 sections, and possibly add a few thermistors, and thus be able to keep a relatively constant temperature (or any other desired heat profile) on the sensor. As it is, the sensor will be at varying temperatures along the single heater winding, depending on the heat load/loss for that section of heater element.