Baby farmer villagers can harvest & plant crops just like adult ones. This is NOT the behavior in Java Edition.

This bug can be fixed with a change to villager.json in the vanilla behavior pack to make villagers not get the behavior_peasant component group until they grow up. You can't fix the old baby villagers, but since they'll grow up in 20 minutes anyway, that doesn't really matter.

Steps to reproduce:

1. Spawn a baby farmer villager.
2. Create some farmland around it and throw carrots/potatoes at the baby farmer.
3. Notice how it starts planting and harvesting the crops.

(Note that the baby farmer villagers are affected by MCPE-20278 just like adult farmer villagers.)