At DTW I ran into issues trying to board using the transit without visa program for PVG, because my stop in NRT on the return was only a couple of hours. Someone above a red coat was called to come by (not my request, gate agent's own volition), who agreed that I should not be allowed to board. I insisted repeatedly that they call global ticketing support/assistance. Eventually the agent agreed to call global, and global ticketing approved the itinerary for travel within minutes. Obviously this strategy isn't too useful after the fact, but if they run into this again, asking the agent to call global could be a good strategy.