You could make the same mastery argument for farm animals, feathers/lobsters/fillet, etc.
Every product is tied to a time value in the game, factoring in the ingredients down the line to the crops and animals. Just a guess here, but i'm thinking they factored in only machine mastery from the beginning, not the crop/tree/bushes/animals/fishing mastery, and readjusting the time value for these will necessitate a re-valuation of the entire product chain. So anything that was not created with time mastery is unlikely to get it.