Alright,
First off, Yoyo is correct. There's a reason we publish GR irregularly and hesitantly, and it's because, in addition to the fact that we're not entirely comfortable with the system when it is working as intended, it's also run using an old piece of code that none of us are intimately familiar with, so it's difficult for us to add site changes into it. I'm working on making it accurate for all games (SoS, unranked, and the ten player variants) now, but that may not come as quickly as some would like.
Second, it wasn't our intention to mislead you. This was a miscommunication, and it's my fault, so I'd like to apologize to all of you for that.
@Zybodia, Elo doesn't have dropoff over time, and GR is basically just Elo extended strangely to seven players.