Say 5 different people take the plumber's license exam in different states.
They all proceed to become Masters.
I ask each of them the same question.
I may only have 2 of them agree on an answer.
Plumbing code and building code are to some degree, variable by the area that you are in, and further complicated by the state's own code restrictions.
As long as you guys keep things civil and, even better, friendly, there wil be something for everyone to learn.
The siphoning thing is a valid point, but the garbage disposal connection is well above the dishwasher drain, so it surely won't evacuate all the water from the dishwasher. BUT how much water flows back into the dishwasher after the drain cycle is complete? Is there a check valve in the line to stop the backflow? I have seen nasty stinking water in the bottom of a dishwasher before, does that indicate a plumbing problem?
It seems to me that an air gap should settle the drain quicker, and with less drain pipe, it should return less water into the dishwasher drain....right?
I ain't no plumber, I got questions too!