The performance preset is the default benchmark. The other presets are made for reviews, so you don't have to enabled FSAA, AF, high res by yourself, which makes benching a zillion video cards less time consumpting.
Furthermore Performance is the only mode basic users can see a score, so adding performance and reward points for it would be the only option that makes sense if you want to add Vantage. Without rewarding points, you can as well add all presets, because nobody will care anyway.