I just read this:
http://www.maxsportsmag.com/science/issue40/40sci2.htm

Basically says that undenatured filtered whey does not mean lots of good protein subfractions since the good stuff could be filtered out along with the milk fat, and the denatured portion could simply be centrifuged and tossed out. And whey proteins from cheese/casein factories have most of the good subfractions missing presumably due to cheese making processes.