I'm not sure if the devs are removing some of these blocks, but if you didn't know, double stone slabs have a hidden block state called 'seamless'. This is true for most slab blocks. Now, the awesome thing about these block is that mapmakers can retexture them to be whatever they want and they can't be obtained in survival. They aren't different from regular double stone slabs by default, but if you think about removing them, please reconsider. They aren't useless to us command makers. Thanks!