no, a rubber hose gets weak over time
they all used to have a spring in them,but todays rubber is more stiffer,heat,oil,ozone resistant and last longer,there for will not suck flat as often...but they can and do...even a new one can,IMO
the pressure cap help build presssure and combind with anti freeze raise the boiling point, the pressure helps force the water into the small passages to keep hot spots/steam pockets from forming in the heads
the pump does move a good bit of water at idle,but when the revs go up,its sucking harder than it can push the mass of water through the restrictions in the engine cooling sytem
the sucktion build up and sucks the hose closed
I use a sainless wire so it does not rust my self and wrap it around something a little smaller that the ID of the lower rad hose,I make it long as the hose
I have dug a many of rusted up pieces of spring from out of the pumps and even had some wraped around the impellers over the yrs
with a weak hose you can stand there and rev the engine by hand and watch it suck closed
seen this on ferds,chibbys,and mopars