subsidence,
I'm not sure if ALL flaps reduce the stalling AOA. But they all reduce the stall speed (increase in Cl, allows reduction in speed to produce the same lift)
The thing to remember is that when you lower the flaps, you are changing the wing. You are therefore flying a different wing with different stalling characteristics. I do not know what are the characteristics of an airfoil that determine the stalling AOA.
One way to look at it is that by lowering the flaps, you are increasing the downwards angle towards which you are deflecting, requiring a creater turn in the airstream (this is what gives you the extra lift.) By increasing the downwards deflection, you will hit flow separation sooner. Rather simplistic explanation. Maybe it might even be wrong.
I welcome any corrections to what i wrote above.
palgia
PS. maybe i'm wrong, but i was under the impression that lowering flaps could both increase or decrease the stalling AOA. (depending on the type of flaps, and varies from wing to wing)
Please correct me if i'm wrong.