You cannot craft polished grimstone slabs, stairs or walls.

What I expected to happen was...:
When you put grimstone in the stonecutter, you can craft all three items. This is what happens with other blocks, such as andesite or diorite.

What actually happened was...:
You can only craft the non-polished variants.

Steps to Reproduce:
1. Place a stonecutter down
2. Open the UI
3. Put grimstone in it