Only God can make the wind blow straight enough over a large portion of this curved planet to explain this.
Time for more coffee.
The bidirectional winds which produced the linear dunes are themselves the result of the location of the southern Hadley Cell and southern mid-latitude converging over that region of Africa where these linear dune formations and the Kalihara Desert are located. This convergence zone happens to be the convergence region between the two worldwide cells where the southeasterly trade winds transition into the westerly trade winds. The transitional period produces bidirectional winds which persist during the season long enough to result in the parallel lines of dunes. This field of linear dunes is a comparatively microscopic area in comparison to the convergence zone of these two world encircling cells.
These natural features are really not at all unique.