These excuses do not satisfy me. First, the Davis lab is one of the best in the country. Second, while it may be true that some iron is introduced during the manufacturing process, it can only be a small amount, like 20-30 ppm. If the equipment were shedding large amounts of metal, the equipment would be rapidly worn down. It is true that there are several forms of iron.
Bioavailable iron is the form of iron that the body is able to use.
The iron in vegetable matter is less readily available than the iron found in animal products. But testing for the different types of iron is either difficult or impossible and how they are used in the body is not entirely understood. There is even concern that a diet too low in iron may eventually cause anemia. I cannot tell you which of these products to feed your birds. There is much to consider besides iron levels.