Does This Debunk the "Coolant Can Flow Through the Radiator Too Fast" Idea???

I have to disagree on one point
To circulate the coolant, the pump must produce a pressure difference between inlet and outlet otherwise it ceases to be a pump.
The pump producing a pressure difference has to be "a thing" in order to get some coolant circulation.

some pressure is also necessary to avoid cavitation, doesn't matter what causes it, but you need some, it makes it harder for the pump to thrash the coolant so hard that you create bubbles of vaporised coolant.
you need something for the pump to pump against which is why, as you say, a thermostat or restrictor is useful.

a cavitating pump produces an area of massively low pressure around the impeller which is much more attractive than going out the exit, you end up with a self perpetuating vortex like situation. low pressure promotes cavitation which promotes low pressure, hence a cavitating pump produces little pressure difference between inlet and outlet and hence greatly reduced coolant circulation. at least until the pressure in the system raises considerably and puts a stop to the situation.

that may not happen with a coolant that doesn't cause a pressure increase when overheating