Does your coolant temp drop when you turn the heater on max?

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2017 CX3 AWD
One thing that I have learned after a cooling disaster on my MINI is that by turning on the heater, the coolant in the heater core gets to mix with the rest of the fluid and helps bring down the temperature slightly.

Now that I am watching the temperature of the CX-3 more closely, I tried this and nothing happened. By turning the heater on max (max temp and fan, nothing sophisticated on my Touring). After five minutes of running like this at 65-75 mph, the coolant temp continued to fluctuate as if the heater was off. The heater was blowing hot though. Is this normal?

I am 80% positive that I tried this once last year and the temp went from 212 to 190 in stop and go traffic. There is a 20% chance that my memory failed me and that it was in the MINI.

Any insights are appreciated.
 
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