As I understand it in simple terms, the center of lift migrates I/B with speed. Slow and heavy clean would put that lift at the wingtips, flaps extending would bring that lift I/B loading the flaps transfering the vortices to the extreme usefull camber of the wing "flaps".
Great experience of this is on a misty/light rain day (747 fowler flaps my favorite), it is easy to see. You can see the vorteces increase I/B as the aircraft approaches and is on it's landing rollout.