All double half-slabs (except for wooden ones) render as double Stone Slabs

I was building a bridge with nether brick slabs. I created a double half-slab when something funny happened: it rendered as a double stone slab. I tested this with the other slabs in the game, and all of them had the same result: rendering as double stone slabs. Oddly enough, "Pick Block" isn't affected. I also discovered that this glitch does not affect wooden slabs.

Steps to Reproduce:
1. Put two slabs of the same type on top of each other to create a full block.
2. That's all it takes. You should see the glitch occur.