I've never heard of a single eligible person being denied transit without visa (i.e forced to go back where they came from) in China. You seem to be conflating TWOV with permission to enter the country during transit, which is discretionary and, often not granted during daytime layovers < ~8 hours, in cases where remaining in a sterile area is possible.

Sterile transits are not possible if you have to change airports or terminals (some exceptions here), but if you are connecting in an airport like CAN where airside transit is relatively seamless, and want to go outside, consider reserving a day use hotel room and/or come up with a compelling/flattering explanation on how you plan on using your time.

On the whole, China is quite liberal at granting entry permits compared to other countries that offer TWOV (e.g. Vietnam, Saudia Arabia, India).