dirt block digs fast

Put the summary of the bug you're having here

[I wrote using Google Translator.]

 

What I expected to happen was...:

What actually happened was...:
While holding down the left click, If you break the grass and break the dirt block, it breaks quickly.

Steps to Reproduce:
1. take a stone shovel
2. Press and hold left click
3. Break the grass
4. Then break the dirt block