It was mentioned in the 1.16.220.52 beta changelog that waxed copper could be smelted in a furnace or blast furnace to remove wax, however that doesn't seem to be the case. No form of waxed copper block can be smelted, at all.

Both of the below things were said in the changelog, and they kinda contradict each other.

• It's now possible to de-wax Copper using furnace
• Waxed copper block variants cannot be de-waxed using furnaces or blast furnaces

changelog: https://feedback.minecraft.net/hc/en-us/articles/360058166892

Something here is amiss and needs correcting haha