That sounds like an interesting wrinkle. The (odds of a) round closing could also be sensitive to the in-rush of sealed bids or even how different later orders are from earlier ones. That might help ensure an early-close either just before, or just after, a wave of orders that hints at information the earlier-bids didn't have. (That is, tick the unseal-matching process based on a signal of substantive change, rather than only wall-clock-time.)