Micellar casein, when consumed, clots in the stomach, forming relatively large globules of protein that empty from the stomach much more slowly than acid-soluble whey protein and is thus digested slowly
In fact, the relative lack of difference in aminoacidemia reported by Reitelseder et al. between their whey and casein conditions is, in all likelihood, due to their use of calcium caseinate. Calcium caseinate, as distinguished from micellar casein, is soluble (and is thus used in numerous food processes), and so digestion rates of this form of casein are not likely to be overtly different from those of whey