Yeah, welcome to China Ask them where the complaint office is...

Seriously, there have been many problems reported with Chinese airline partnerships with US airlines... worse things like: not being able to get mileage credit, having award tickets mysteriously cancelled with no notification, etc... lounge access or seat assignments are the least of the problems.

Having a business class reservation can improve your odds much more. The term "VIP" is something you want to try and use in communication with them to get access to higher level benefits. Be sure to have documentation in writing (card) of your status as well as documentation from that airline on partner benefits in hand.