It is an incorrect use of what was already a flawed metaphor. Pressure is isotropic. Directed pressure makes no sense, like all other fluid analogies in unrelated fields of engineering.
Wait so cross ventilation, where a breeze will flow through a house if windows are open on opposite sides at a much greater rate than if windows are only open on the upwind side… isn’t really a thing?
I took the analogy to be about the location of the pressure and not the direction. If you allow pressure to build on the input pipe when you can't accept more, the component that is upstream in the flow is able to observe that and respond. Maybe the difference is I envisioned a series of pipes and not a single one.