Being flagged as a "New contributor" on one site when they are already an experienced contributor contributor on other sites in the SE network seems a bit silly. I might treat a brand new user to the SE networkSE network a bit differently as they may not know their way around, but if a user already has 30K rep on another site then I really don't want to be wearing my kid gloves and start explaining the basics (which could also come across as rather condescending).
But I also don't see what this provides that the existing rep score doesn't (as others have already mentioned)?