Pickaxes don't speed up piston breaking

Summary:
Pistons cannot be mined faster using a pickaxe than using bare hands, even though their material is stone.

Steps to Reproduce:

1. Place down two pistons
2. Change the gamemode to Survival
3. Mine the first piston using your hand
4. Mine the second piston using a pickaxe

Observed Results:
The mining speed is not faster when using a pickaxe.

Expected Results:
The mining speed should be faster when using a pickaxe.