While wake will descend, depending on conditions, they really only go about 500 feet. There are many images and video that show A380 and other wake, and most of the time, the energy is in the rotation, and sink is a function of the weight and associated pressure.
In regards to KH waves...isnt that more washboard that roll?
Given what what was reported, vs the actual from the manufacturer, it is difficult to believe much at this point.