Grass blocks randomly placed on the old chunks

World was converted from 1.11.2 to 21w43a. In old chunks grass blocks was randomly placed on the ground.

Reproduce:

• Create a world in 1.11.2.
• Fly towards beaches near the oceans
• Convert it to 21w43a

Observed Result

Some grass blocks/dirt blocks randomly placed on the ground

Expected Result

Grass blocks/dirt blocks don't randomly placed on the ground