Right now, slabs mess a little with the x-rays.
Example, if you build your roof using slabs, when in any of the x-rays, it will not be invisible, thus blocking your view to the inside of the house.
This is not a bug, as the game correctly hides only the roof.
But it would be nice if the code also checked for slabs as roofs. When they are the top most blocks, they are for sure used as roofs, right?
The floor also has a few problems when made with slabs. A 3 layer floor for example will show only the bottom most layer when in the “all walls down” vision (second x-ray mode).
Again not a bug, the game is doing it right.
But it would be better if it could consider all bottom layers as one solid block for the floor.