I left this thread to log in, and when I got back I found that Send Clowns had already given the answer. However, here's my tuppence worth.
There can be no lift on an airfoil, or no thrust on a prop blade, unless there has been downward (backward) momentum added to the airflow. So no downwash - no lift.
This downwash can be induced by a straight change of direction of the airflow, as in a flat plate with positive angle of attack. It can also be induced by pressure and speed changes over cambered wings. As Clowns says, two parts of the same effect.
Dick W