Confirmed that it doesn't work for me either.
I wouldn't put it passed Mojang to just... forget to toggle them. 😛 They do development like a 10 year old ADHD kid who refuses to take his Ritalin. "I'm going to make Lecterns. Oh wait. I'm going to ride my bicycle."
It's bad game development because they rolled out effectively 1/4 of a feature. This kind of thing would be acceptable if the game were in Beta, but since it's supposed to be a "released" product, there being features that are half-rolled out just makes the development cycle seem sloppy and apathetic.
So... bad game development then? 😛
Except that there are no Nether Brick Slabs accessible in Creative mode.
What good reason could they have for making Wither Skeleton heads drop from Wither Skeletons, but not having Creeper, Skeleton, and Zombie heads drop from their respective mobs?
http://www.minecraftwiki.net/wiki/Head
It'd be fine if they were rare. They're impossible to obtain in Survival.
Does it with a clean jar for me. A fresh dev build.