In a weird way this makes sense to me. A lot of what takes water out of the ground is plants with their roots that extend way, way down. No plants means no root

In a weird way this makes sense to me. A lot of what takes water out of the ground is plants with their roots that extend way, way down. No plants means no roots and no shortcuts to get the water out. It has to go out the old fashioned way by diffusion. The thinker the dry layer the more "insulating" it is from a water diffusion standpoint. It's kind of like lake ice. The thicker it gets the slower it gets thicker.