Some blocks do not cull the faces of the same block if it is placed next to them, making large areas of this block appear as tiles.
Last updated for 17w06a
MC-109087 Faces of some blocks are not at all culled when said face is hidden by a solid, opaque block
MC-64702 Cullface on snowlayer not working properly
MC-114779 Stairs render faces that cannot be seen normally