Copper Stair Duplication

Copper Stairs are duplicated in the stonecutter

What I expected to happen was...:
When I went to put weathered copper block into the stone cutter I was expecting 1 stair to be outputted but I received 4

Steps to Reproduce:
1. opened a creative world

2. tested each form of copper block in the stonecutter

3 found each form of copper block turns into 4 stairs.

 

(unsure if this is intentional)