Now those words sound extremely familiar? Care to site your source?
My point, I have already said alfalfa is somewhat digestable, but very well. It is not preferred by rats in any of the studies, and in the case of purina, i would imagine the use of dehydrated alfalfa is just like you said. For the sake of keeping other rat breeders from buying the cheap rat feed because of the main ingredient being alfalfa, there is nothing wrong with saying that alfalfa is not good for rats.
If you wish to make your point, you should put the whole study without any cuts. I've read the article your referring to, and while you may have gotten the gist of it, there is more information to be had on the entire study that you left out.