Villagers only plant Wheat

When Farmer villagers harvest potatoes/carrots, they plant wheat.
Steps to reproduce
1. Go to village with farmer and farm with potatoes/carrots.
2. Study them harvest the potato/carrot.
3. Notice how they plant wheat instead of the potato/carrot.

I searched and found nothing. Only similar bug report is
https://bugs.mojang.com/browse/MC-45480