Airbus and Boeing wing design is quite different if it comes to high lift configuration. While Boeing is using tripple slotted flaps (with the upper surface of the third flap almost perpendicular to the fuselage longitudinal axis at max deflection), Airbus uses just single slotted fowler flaps at smaller deflection angle, but with very high efficiency.
So if you understand extending the flaps as virtually turning the wing relative to the fuselage (turning the zero lift angle of incidence), Boeings "turn" their wings more than Airbus, thus needing lower fuselage AoA.