Chinese transit without visa requirements are fairly simple, but very lengthy in their wording. This is mainly due to a string of exceptions and minor variations on eligibility and routing.

Airlines - other than those agents actually at the desk on check-in - are generally not a good source of visa or visa free transit advice. They simply don't know the rules and don't have the time to look them up. Or take the chance they are wrong. So they often advise a visa is necessary even if it's not.

'Official' Chinese TWOV sites are often way out of date. Until recently some were still listing Beijing as only 72-hour TWOV when this changed a long time ago. They also don't necessarily have all the information from the individual provinces who seem to drive their own membership of the TWOV club (with different rules and eligibility between them).

Short answer is to ignore airline or visa site advice and use the resources of somewhere like FlyerTalk to get the most accurate information.