Fatty acids + sulphur. Why not veg?

Scotts Natural Fungus & Bug Killer contains fatty acids+sulphur. When I first picked up the bottle I thought it would be a good way to slow down blackfly and powdery mildew on courgettes but the label says it is not for vegetables. Does anyone know why this should not be used on vegetables.?

That is what the label says but to my way of thinking fatty acids are the active part of insecticidal soaps and sulphur sprays are OK on veg.

Does anyone know about these things?