Yes, that may well be the case. However, the wiki example calls out the need to use the metadata parameter explicitly and FurnaceRecipes over GameRegistry:
"You may have noticed that the input does not accept a metadata or damage value. This is quite silly, but the GameRegistry doesn't have an addSmelting variant that takes metadata. For that, we will need to input FurnaceRecipes, get its instance, and then use its addSmelting method.
The example here is burning black wool to get white wool.
FurnaceRecipes.smelting().addSmelting(Block.cloth.blockID, 15, new ItemStack(Block.cloth, 1, 0), 0.1f);"
Is there an equivalent now, or doesn't it matter?
And thanks again for your help. It is much appreciated.