So afther this bug and its fix MC-156306 villagers wont share bread unless they have more than 24 in their inventory.
Back in version 1.14.2 and earlier, they used to share when having an ecess of 6 loaves.

This makes villager wheat farms rather inefficient in regards to villager breeding since each harvested wheat only produce one wheat and the villager needs 3 wheat to craft a bread and wont share enough bread with another villager for breeding until it has crafted a total of 27 bread which again requires it to harvest 81 wheat.

It is easily testable by inspecting villagers inventory with commands when giving them bread and see when they begin to share with another villager.

The screenshots shows that the villager on the left have 24 bread in its inventory and wont share any with the villager on the right, but when it recieves a 25th loave of bread, it will share it with the villager to the right.