I would generally not take a tourism web too seriously, nor even an airline - because when I check in the conscientious agent will check TIMATICWEB. I hope, as sometimes the agents are wrong - some threads indicate the lack of understanding on behalf of agents check pax in for under 72 hour China transit stays as attempting to deny those pax without China visas, when none were needed (particularly when the PVG/SHA and PEK 72 hr TWOV became available). (Showing the TIMATICWEB rules made a difference for at least one or two, iirc.)

It's a PITA - but in this case, the issue of Americans traveling abroad - even to some US territories - passports have been required for some time, iirc. Carrying mine makes it easier, particularly given I am not USA-born.