Quoted from apositive
I don't know for sure . . . but agree that casein is part of the milk and thus not listed separately, nor can those neutrals - yogurt, ricotta, mozzarella - be rendered casein free. My guess would be that the status has something to do with how much casein is precipitated out in processing these foods and thus how concentrated casein is in the final product; also there may be other factors in these foods that balance out any negative effect of the casein.
Clear as mud, huh?
I think this is the sort of argument that Heidi was using as aforementioned.