CAN break blocks w/sword in creative

What I expected to happen was...:
Nothing would happen when I hit the ground, and the mobs would die in one hit from my Sharpness X and Fire Aspect II and Knockback X sword.

What actually happened was...:
The block I hit w/the sword vanished, and it dealt the same damage as punching.

Steps to Reproduce:
It might not be this complicated, but this is what I did.
1. Set up a custom generic villager to give you a named and lored diamond sword with huge enchant levels on it with /summon
2. Trade with it.
3. Use the sword on a mob and find it deals the same damage as punching
4. Hit the ground with the sword and find the block breaks instantly.