The whole point of rating a recruiting class these days is to evaluate the level of talent that is being brought in for any calendar year. Whether they are high school, prep school, JUCO, or transfers, (grad or otherwise) should make no difference. In fact, I would argue that anyone above a HS graduate is more experienced against a higher level 0f competition and should be evaluated with this in mind. I believe that the present system is a long way from perfect, but this seems to be the biggest flaw.
However, I also remember time that recruiting classes were evaluated on additional criteria than level of talent. The most obvious criteria was filling areas of need or replacing people on the coaching staff... but as mustache was fond of saying, "that's another story."