Isn’t this kind of the same thing as saying the pump creates the pressure?
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For rotodynamic (spinny) pumps, the impeller technically doesn’t pressurize (squeeze) the fluid. Instead it adds velocity / kinetic energy to the fluid, making it flow. The volute (pump casing / housing) geometry reduces in area as the fluid moves around to the exit of the pump, which converts some of that flow energy to pressure energy.
Think of putting your thumb over the end of a hose. In either case you have flow, but when you restrict the opening you get a much higher pressure stream coming out of the hose.
You can contrast that with a piston pump, which directly squeezes the fluid.
Of course, to a certain extent this is an academic distinction. Ultimately the pump works by adding kinetic energy to the fluid, but the pump also converts that energy into pressure, so in a sense the pump is creating pressure. There’s also the fact that flow, pressure, and resistance are all interrelated and affect each other. If you are running a pump at a fixed speed and you increase the resistance in the system (piping) then the flow will go down and the pressure will go up. So they’re interrelated.
If you are at all familiar with electrical circuits, flow and pressure are analogous to current and voltage. You can’t have flow without pressure and you can’t have current without voltage, and it’s the system resistance that links the two.
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