Well, you could not open a Maytag while it was agitating to add anything. Maytag had so many complaints about bleach damage to fabrics because of the poor agitation and the fact that it stopped when the lid was raised, that they came up with the delayed bleach dispensing system in the TOL washers. Machines without the dispenser had the directions that the user measure the bleach (up to a cup)into a one quart container then fill the container to the top with water. While briefly lifting the cover, you were to pour the water around the agitator and immediately restart the washer. The lint filter agitators were a definite plus in this case because the agitation would cause the bleach solution to be drawn into the agitator and dispersed at the bottom of the tub. While Maytag maintained that it was more important to move water through the clothes than clothes through the water, which is not completely true because you need both, in the instruction booklet I have for the 4 AM, it cautions that any item added after agitation starts should be completely submerged. That was just a hint that the agitator action would not pull it under.
Detergent burn was a real danger with the early and highly caustic detergents and could very easily happen with detergent sprinkled on top of the clothes load. I, too, think having it on the bottom would give a better distribution and ensure more rapid dissolving of the powder. My mom was used to Maytag wringer washers where you filled the tub, started the agitation, added the detergent, then the clothes. That was the way she loaded both of our Kenmore automatics.