MC-124909 was fixed, however if you relog before removing the output item, no recipe is awarded
- Obtain iron ore
- Remove the smelt iron recipe from yourself (/recipe take @p iron_ingot)
- Smelt the iron ore in a furnace
- If you remove the iron now, you will get the recipe/experience as expected
- Relog first
- Remove the iron; no recipe or experience are awarded
Armchair analysis is that the "recipe used for smelting" is saved to the furnace block entity somewhere in memory but isn't serialized to NBT, so it's lost when the furnace is unloaded.