how the water gets out thru that drain
There is a solenoid-controlled lever that will pop the drain plug up, allowing the water to drain. It's not a very good shot, but in reply #7, the solenoid and part of the lever mechanism can be seen on the right hand side of the drain tube.
This is the first gravity-drain dishwasher I have worked on (although the 1950 Youngstown Kitchens Jet-Tower might be....) - not familiar with these at all .... yet!!