I wonder why you are not directing your complaint to the Pudong International Airport authorities, and/or the Chinese government, when they are responsible for airport operations and visa-issuance procedures.

The information provided by UA (via IATA or whatnot) was and still is 100% correct. You do not need a visa if you have a connecting flight within 24 hours. This past May, I went to PEK with an expired visa, and was issued a 24H visa on the spot because my flight arrived late and had to take the next day's connection. I went into town and had Peking duck that evening. Maybe China had changed the rules and/or procedures since then, either nationwide or specifically for PVG, but that's not UA's doing. Perhaps this is your lesson that in China, official rules often and do change on a whim.

In any event, it's up to you to ascertain the proper documents before departure and not base it on information provided to you at the time of booking the ticket.