Sorry but I never subscribed to the "when you get stamped in at border control" and that is not my personal interpretation. The rule is very clearly scheduled arrival to scheduled departure. That will definitely be what's needed to argue your case for boarding at your origin. So to notenut, being 3 hours over that 48-hour limit from the get-go, likely won't cut it without a visa. You may be left sitting in ORD.

In this particular situation, I also wouldn't bank on the benificience of Chinese immigration. Redo your itinerary to fall within the 48 hour arrival-to-departure rule. And this assumes you are a US citizen or other citizenship entitled to 48 hours instead of 24 at PVG.