I don't find that surprising or scandalous. Wheat is (approximately) fungible, so if you produce more for yourself, you're decreasing the marginal demand for wheat in the market. Besides, barring everyone from overproducing wheat makes more sense than only banning people who somehow intend to sell the wheat:
1. Intent is hard to prove or judge
2. By not applying a blanket ban, you're unfairly hurting net consumers of wheat, or farmers who can't internalise their wheat consumption and rewarding those who can.
I'm having a hard time seeing how the blanket ban was wrong in any way.