After doing some testing in game, I have found a few things. For the chef job now, players have to manually input items to be cooked in order to get paid for the job. If either a hopper or dropper input any items into the furnace - whether it be to refill the items being cooked OR the fuel to burn, the players 'ownership' claim on the furnace will be erased. Hoppers pulling the cooked items out of the furnace have no effect on the ownership. All furnaces I've tested seem to work this way at the moment (unenchanted, Eff. 1, Eff. 12, Unb. 6, Fortune 1, Ultimates). For inputting items, both shift-clicking stacks and using the new furnace crafting book work with getting paid for the job. This is speculation, since I'm not an alchemist I can't test it, but I assume Brewing Stands also work the same way.
This has indeed been done by the plugin dev, it is in the update to 1.13, sodly nothing we can do about D:
