Well, I remember taking an anthropology class in college and they talked about the parasites that live inside organisms and how many organisms reproduce via copulation because it increases genetic diversity to help combat said parasites as they become acclimated to the body they reside in.
So, with that in mind, the more recently deceased the animal, the more likely current parasites will adversely affect the cloned animal, right? So maybe the thinking has to do with that. Just a thought.