Neptune recirculation pump
When they installed recirculating pumps, it was made to recycle the water from the bottom of the pump.
When detergent is added to the dispenser, the soap immediately runs to the lowest point- which is the pump as well as the first of the water that enters the machine. Maytag fixed that problem by using 100% of the detergent that was added to the washer. Where before, some detergent was lost.
In the later years, they added a plastic “tray” before the hole in the bottom of the outer tub. It would catch all the detergent, the motion of the tub and water would eventually mix all the detergent.
Whirlpool Duet’s claim is direct inject. The water would mix a little in the dispenser and shoot it directly in the tub full of clothes. They also had a little plastic ball in the “hole” of the outer tub, as the water would raise. The ball would rise and “plug” the hole- in order to use all the detergent in the wash tub.