It's a combination of straight flow and rotational flow - the rotation goes from under the wing, around the leading edge, over the top surface, and down off the trailing edge - see the beautiful attachment point on those smoke lines, with the initial part of the airflow over the wing coming from underneath, not in front.
Try it yourself - blow up a ballon, and try to push it forward.
Now try it again with some backspin, and watch how it climbs and moves forward, having deflected the air down and back. Add frontspin and the balloon dives at the ground big time.
Sticking your arm out the window is a simple example of deflecting flow, without the rotation- the air is deflected down, and your arm goes up and back, the total reaction. This can be split into lift, and drag.
The rotation comes from the aerofoil shape, which makes the straight Newtonial deflection into a rather prosaic rotational flow with streamlines, inflow, downwash and angels singing. Mr Coanda joins in the chorus.
