Mob griefing is set to true, so the villager is able to break crops. The first 4 inventory slots are filled with seeds, and the last 4 are filled with wheat. When the final slot contains wheat, the villager will no longer harvest crops. In prior versions, the villager would harvest, but not pick up the crops. (Note - I have also not seen the villager toss excess food to the other villagers in my test scenario, as well as the occasional farmland block left unplanted). This enabled farms to have hoppers, or hopper minecarts pick up the non-collected crops. The villager will replant if all the crops are harvested manually.

Suggestion - Use the composter if more than 1 stack of seeds/crop is filled and there's no villagers to toss food to.

All inventories are full, so the villager simply stops.

 Test setup -