I guess I find it bizarre that the concrete block (which has the same texture ID mind you) used in creative when making prefabs, ends up being the same concrete flavor in all biomes, but when you craft one [or use creativemenu] and place it somewhere in the terrain, it morphs into that biome's topsoil appearance. There must be some hard-coded conditions that set the texture on a player-placed block with this new MM system as opposed to when the concrete texture block is placed in a prefab or part of the region generation.