What they mean by "increasing wetness" is that is lowers the surface tension of the water, so that it soaks in, rather than beading up and running off the surface. Rinse agent in your dishwasher does the same thing, but with the goal of getting the water off your dishes before it can dry and leave a mineral deposit. There is a product called "Water Wetter" (I think that's the name) for car radiators which does the same thing, so that the "boundry-layer" of the flow is thinner, so that heat transfer is maximized.