This is a good thread with valuable discussion.

I am late in reading it.

My take away:
in the future when giving advice
urge the original poster to use two thermometers to measure at the inlet and outlet of the radiator,
either by inserting a thin probe inside to touch coolant at the hose slip on joint,
or by touching two aluminum or brass radiator fins.

There have been hundreds of cooling discussions on Moparts
and this basic point about getting good engineering data has been seldom mentioned.

It is even more true in freon HVAC system where before and after temperatures and pressures are “industry norms.”

It is related to the joke:

Dentistry costs money,
lack of good Dentistry costs even more money.

(because the bacteria P. gingavalis that attacks the gums also attacks the lining of blood vessels throughout the body, heart valves, and maybe the brain itself)