Pretty much correct , except that a water hose doesn`t work exactly a pump . The hose has no internal bypass ( unless it ruptures
) . If you put a variable cut off valve on the output of the hose with a pressure gauge teed in and close it , you will see whatever the system pressure is . Watch the gauge as you open the valve and you will see the pressure fall off as the flow increases .
In a hydraulic system , if you have enough hp behind the pump , you can push as much flow through the orifice as you want up to the flow capacity of the pump . You just increase the pressure drop ( delta p ) across the orifice . The reason pump flow drops off as pressure increases is because all pumps have internal leakage from clearance between the gears to housing , pistons to sleeves and housing etc and on diaphragm units ( fuel pumps ) , across the check valves . Other components in the system can and do have internal bypass/leakage . All pump circuits have a relief valve somewhere in the outlet ... or you will have a disaster if the output is closed off totally . I`ve seen gear pumps literally explode when the output was blocked .
Bob