Since OG is technically the gravity in the fermenter, that is what the program is giving you. I agree that with top off being a part of some brewer's regular practice, that it would be good to have a post boil gravity target as well. Brad made the adjustment with the post mash versus pre-boil gravity so that people who add extract or other sugars could get an honest target for what they should expect out of the mash tun. It would make sense to do the same on the tail end of the process.