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
Thank you for your report!
However, this issue has been closed as Working as Intended.
Thanks for mentioning this bug! We had some conflicting information in the changelog, but this has been rectified now, and the line that mentioned the following is the intended behaviour for waxed copper blocks:
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