Technically the flap deployment leads to an increased AoA (chord line "pitch up" while lowering trailing edge devices). At the same time flap deployment increases drag, which reduces TAS at a fixed power setting, which requires an even higher AoA to maintain the same lift.
Bank during a turn increases g-load demands and hence needs a higher AoA to produce the same lift at a given speed.
If you would have been riding at or near the max AoA prior initiating the turn you might get into trouble. If you are in a deceleration "flow" the adding of flaps might cancel out trim requirements during deceleration, hence leaving you with a "minimum effort manoeuver".
Split flaps are an additional problem. Thatīs harder to recognize and to handle in a turn (as compared to straight and level).