Just look upthread, all the confirmation you need is there.

The Chinese airlines use their own GDS called bluesky. As part of the internal Chinese travel market trip.com has direct access to bluesky.

Other websites are typically integrated with the western booking engines like Amadeus and Saber, and whilst the Chinese inventory is available and quotable there's an extra margin applied hence why the prices are higher.

Of all the OTAs out there, trip.com is being bankrolled by the Chinese government to be a decent online travel agent, they have functional customer service (the occasional agents have their moments, so HUACA) so fill her boots and book whatever you need.