I'm trying to see if CZ itself is at fault.
CZ's website does not provide links to Timatic.
It does have a page called "Visa", but does not have any information regarding China:
http://global.csair.com/US/GB/INFO/CXZB/PAVI
Then it has this page (
http://global.csair.com/US/GB/FLUS/ZZFW/GJMQ) about "visa-free transit". However, it mentions how CAN-WUH-SFO and other one-stop flights will exclude you for 72 hours. There is nothing about 24 hours or the special WUH restrictions. And the embassy/consulate pages say nothing about it.
Then we must ask, why is CZ in the business flying WUH-SFO if WUH has this restriction? There should be a USDOT complaint filed already!