Please take a close look at the photos on the site. Especially the ones with temperature measurement. Pay attention to the DMM setup and diagrams.
The following are my thoughts to detecting the tc an heater on the C245/C470. Please let me know if there is an error in my assumptions.
A resistance measurement only tells us where the tc alone is connected. This is due to the fact, that the tc has an internal resistance of a few mR, which is in the range of the contact and cable resistance of the measurement leads. If a resistance in the Ohms range is detected, we can't know if it is heater alone, or heater and contact resistance, or heater and tc or ... . Hence ~0 R -> tc only, >0 R -> heater or heater in series with tc.
A voltage / temperature measurement only tells us where the heater alone is connected. This is due to the fact that the burden current of the voltage / temperature measurement is so small, a resistor with a few R doesn't change the voltage too much and we don't know if it is the tc alone, or tc in series with heater if the measured temp. is above ambient. However the heater doesn't generate a Seebeck voltage between the leads, thus it shows 0V / amb. °C if we connect the DMM to the heater alone. Hence amb. °C -> heater, higher temp -> tc alone or tc in series with heater.
Applying the above reasoning to your diagram we should see ~0R between C1 and C3 and amb. temperature between C2 and C3.
The picture
http://adgd.ru/wp-content/uploads/2021/01/img5_%D0%A1245.jpg shows 0R between C1 and C3, which corresponds to your diagram, ambient temperature is between C1 and C2 however. Hence tc is between C1 and C3 and heater is between C1 and C2. The polarity of the tc checks out, the tc- is connected to C1 in both your and adgd.ru's diagram.
I would appreciate it if you could show me any errors in the above reasoning, however if there are none, adgd.ru's is correct.