I think that what @dcslatter means is that he works on all the people with changes who are already matched between RM and Ancestry before moving on to new/deleted people.
This is very often what I do as well. Of course, you can use the screen for the matched person to add new relatives (parents, spouses, children). After having processed all of these, I usually move on to other new people to add, taking care to find any marriages that I might otherwise have missed.
As I often work in this way, I suppose that this proposal would help me, but think that I would rank it lower in priority than any of the items listed in my proposal for treeshare improvement.