If you right-click a Waxed Copper Door/Trapdoor with an axe, you will get the "Wax Off" advancement if you haven't got it already

The issue is right-clicking it with an axe doesn't actually take the wax off a Waxed Copper Door/Trapdoor. You have to right-click and hold shift with an axe to take the wax off.

The Problem is you aren't suppose to get the "Wax Off" advancement by only right-clicking a Waxed Copper Door/Trapdoor since that won't take the wax off