Redstone lights will go out when they are steps, but not when the lamp alone is

Please describe the issue with screenshots and words attached to this ticket.

Better description (can totally confirm it):
Placing an upside-down slab above an activated redstone lamp blocks the light. This is because Mojang changed upside-down slabs and stairs to act as solid blocks so you can place Redstone at them. It's maybe not "working as intended", more like "working as designed" 🙂

The redstone lamp won't go out, the slab simply blocks the light.
It doesn't matter if the slab sits on the lower or on the upper position, it occupies the whole block.