This only works because this guy's tiles can be rotated without looking weird and he's on modern hardware that can freely rotate sprites with little cost. If your tiles are shaded or have patterns that look different when rotated then it does not work for you. If you are working on a game for the Nintendo entertainment system then it won't work either because you can't just rotate a tile.

The point is not to minimize texture/memory usage. It’s to minimize work for the artist.