You don't mention the route, but it seems it is a two sector flight, so at a guess check in will be at an outstation rather than a hub in China and most likely contract check in agents for MU who do the same thing for all airlines they work for. It won't be an issue. There are plenty of threads on flyertalk with similar queries and answers.
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MU are right that if it's going to be changed Expedia have to fix it as it's their ticket until it goes under airport control around 48-24hrs before departure. You can waste time on phone to Expedia but I would leave it.