Centro paced Natosha Rogers. If you watch the whole 25-mile workout video you'll hear him say he was planning to do pacing duties, possibly for the top American female.
If you see any video of Rogers (there was very little) earlier in the race, you'll see Centro running about 10-20 meters ahead of her and her designated pacer. He's dressed all in black. A lot of people missed that.
Centro was not trying to run his max, but was trying to help out another runner. Once his pacing duties were complete he forged ahead and PR'd by 2 minutes.