The Cambridge video seems to prove the plank theory.
At greater aoa air is wedged under wing producing greater pressure because it can't escape behind quick enough.
Above the wing a void is created allowing the air to travel faster, thus lower pressure.
The aerofoil shape is just good for strength, reduce drag and produces a differential even at zero aoa.
Always wanted to try and run water over the back of a spoon in a vacuum jar, just to see what happens.
Any Uni types that can show what happens.