When I lit the side of a wither skull the side lit on fire for a split second.
What I thought would happen is it would not lite, but did and then disappeared.
To Recreate
1. Place a block taller than the surrounding blocks
2. Place a wither skull on top of that block
3. Lite the side of the skull
4. There is floating fire for a split second.
Happens to all not full blocks, probably a bug but this might get labeled to working as intended