Rock uses the same texture as landscape. Then actual textures for rock are added on top of that using a world aligned blend node. Landscape texture is using a world aligned texture node for 3D projection in both landscape and rock.
Just to note Maximum Dev that RyanB was proposing not to get the light vector with BP (so he could rebuild the phong shading), he was suggesting an entirely material based solution, using an extra landscape layer with tangent normals switched off (by switching them off in the entire material, and having the normals that do…