You need it.

In order to fly, a plane needs a force to counteract gravity. It also has a surface that you can't get rid of. As a consequence, a pressure differential will exist whenever the plane is flying in equilibrium.

In the case of thrust equal to (or greater than) weight, the thrust exerts a positive pression downwards that creates a pressure gradient in relation to the atmospheric pressure.

The correct expression would be something like this:

"A pressure gradient is required to counteract weight and achieve unaccelerated flight. The gradient may be provided by any onboard device, including an airfoil flying at an angle of attack, a rotating airfoil at an angle of attack, an internal combustion engine with its propeler, a turbine, a rocket, etc."