I've seen them eat specific minerals (not on the end) that correlate to some known deficiencies but I've only been using it about 2 months so far. People I trust believe in it so it's worth trying. 34 of the cows I bought had been on this program for 6+ years and the guy I bought them from was a believer. He gave them nothing but grazed pastures and they never saw a bucket.
My guess is that it's dependent on what they are fed. If we (humans) only ate food we grow the way nature intended it, we would probably know what we need and choose it. As soon as you eat at McDonalds your body doesnt know what it needs since it artificially triggers the wrong signals. My cows don't get anything other than grass with mediocre hay if needed.
It may be bogus but it looks like it works for me. I don't really have to understand why if it works. For full disclosure, we are also feeding free choice raw apple cider vinegar as well.