Im building a massive rail system and need red stained clay. When attempting to smelt red mushrooms to get Rose Red dye it doesn't let me even when forced into the furnace.

I looked at the Minecraft Wiki and it doesn't say that they ever removed this so I'm assuming its a bug that it doesn't smelt.

How to recreate.
1: have Red Mushrooms in your inventory
2: open the GUI of a furnace.
3: no way to smelt it

How to force it.
1: place a hopper above a furnace
2: put red mushrooms in hopper
3: place fuel.
4: doesn't smelt like other untransferrable things can.

(This kind of is reporting 3 different bugs at once but i love the other two so please don't fix them. Just fix the unsmeltable red mushrooms)