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

Bewy said
Some have the wrong idea of the purpose of having a t'stat. It serves two purposes, but only one purpose needs a stat:
[1] It ensures the engine does not run too cool, which is inefficient & causes wear.
[2] It is the restriction in the system, that builds up pressure in the coolant in the engine; the pressure suppresses air bubbles in hot spot areas [ nucleate boiling ] inside the engine; air is a poor conductor of heat & you do not want it in your cooling system. You could use a washer instead of a stat for THIS purpose.

The number on the stat is the opening temp; fully open takes another 20-30*.

True. The T-stat opens progressively as coolant temperature increases. In engineering terms, it is a "proportional-only controller". The temperature does not run exactly at the designed "setpoint". To give more cooling, it must open further, which requires a higher coolant temperature. The is termed "proportional droop". Thus, it is normal for the dash reading to be slightly higher at higher loads (ex. driving fast up a long grade). But, as mentioned, it might take ~20 F higher for it to open fully. If you see higher than that, the T-stat is likely already pegged full-open.

Some have a higher "gain", i.e. open more per deg F increase. One in my 1985 M-B when tested in a pot of water against a thermometer and other T-stats, opened slightly late and more importantly opened sluggishly, requiring a higher temperature to open fully. Swapping in a new one cured my "running too hot" issue.

Some here have stated that the T-stat is constantly opening and closing as you drive. That is how your house HVAC works (on-off control), but would surprise me if true for the engine coolant control. A proportional control loop can oscillate if the feedback gain is too high. If the T-stat truly operates oscillating, you could measure that in the flow similarly varying. Robertshaw surely measures those variables on test benches and doesn't mention such.