Breaking the bottom of double tall grass makes the top half look like a sunflower top for half a second

I was playing lucky block survival (to later realize I was in the snapshot instead of forge) and I broke bottom of double tall grass and it turned in to a sunflower.

What I expected to happen was...:
The double tall grass would just get destroyed, possibly dropping seeds.

What actually happened was...:
It turned in to a sunflower for a half second.

Steps to Reproduce:
1. Break the bottom of double tall grass.
2. See the tall grass top shortly turn to a sunflower
3. Scream "What the heck just happened!"