I'm inclined to agree...it would appear that any amount of wind and ice facilitate and assist the phenomenon, but are not the entire cause.
Maybe its a process similar to glaciation, a movement that creates small moraines, sort of a mini bulldozer effect.Glaciers are ice that have a melt under them because of presure that facillitates the sliding movement.BUt this is not jhow the rocks move altogether.
Perhaps we do not completely understand how glaciers move
either, or we might know more readily how these stones move.