The bug

The floor looks completely dishevelled after some time.

Minecraft intentionally will not tick chunks that are more than 128 blocks away from a player, so grass will not regrow. However, an entity can tick as long as its in an entity ticking chunk.

This problem has existed since 1.13.2.

Steps to reproduce

1. Create a default Superflat world on Creative mode
2. Ensure your render distance is at least 10
3. Spawn a sheep 150 blocks away from you:

   /summon sheep ~ ~ ~150

4. Fly directly upwards and use a spyglass to observe the sheep
   → Eventually, the sheep will eat the grass beneath it