Its definitely not real PROOF:
1. If it was an actual, placed brick, there would be a 1 brick count on the server at all times.
2. If it was an interior file that was shaped to look like a brick, you could find it in the slate rar file.
3 If you open up mission editor on slate, and open the tree to look at the interior files, it only shows the null interior for the floor, meaning that the interior wasn't even modeled, it was just created in the mission editor, its literally just an invisible force field barring you from falling until non-existence
4. Again, slate is just a null interior, it is not a cube, null interiors are flat, the only way to make a null cube is to take 6 null interiors and rotate some and form a cube, but that has not been done to slate, as there is only one null interior file.