Block names are different

I was playing on my survival world, collecting some wood. I went back to my house & crafted some dark oak wooden slabs, only finding that the name was different. I then went into a new world in creative & checked if there was any more blocks/items like this. I only managed to find these 5 blocks .

• tile.stoneSlab.sandstone.name
• tile.stoneSlab.cobblestone.name
• tile.stoneSlab.stone_brick.name
• tile.stoneSlab.nether_brick.name
• tile.woodSlab.dark_oak.name