Incorrect texture at the bottom of the grass block

When you look under the grass block that Steve holds, it has the incorrect texture.

What I expected to happen was...:
For the bottom of the grass block texture to be just dirt texture

What actually happened was...:
There was a grassy texture at the bottom of the block

Steps to Reproduce:
1. Make a Creative mode world
2. Hold the Grass block
3. And look under the block, you will see a grassy texture, though it is supposed to be all dirt.