Think about it.
There is thermal probe in TIM, layer of copper (heater), layer of TIM, layer of copper (LN2 container), thermal probe in TIM.
When you turn the heater on, it would be quite strange if both thermal probes shown the same temperatures. It is rather obvious, that probes will show different temperatures.
Springs are equally compressed, threads are of different length.
I turned off and on the heater under -190 oC to simulate stress.