Sorry, I see nothing in a small hose that supports the "too fast" theory. I see it better supporting my own theory. Search out "white papers" on the topic of block pressure in coolant systems. I didn't arrive at this conclusion by accident.
This is fun! I get to say this twice in a couple days lol Anyways, as a chemist I can assure there is no genuine pressure difference between the upper and lower side of the block because they are both connected and in the realm of science, the same system. By pressurizing them in the cooling system, you lower their vapor pressure, elevate boiling point and depress their freezing point. This transition is equal in all areas of the cooling system because when the thermostat is closed, their is still a path of travel through the radiator. Yes, there can be higher pressure areas due to temperature (compare inside the block and inside the radiator) but not enough to change vapor pressure. We can show this using the Clausius-Clapeyron eq. ln(p1/p2)=(delta heat of vaporization/gas constant)*((1/T1)-(1/T2))
