回複：最難防是自己人? Good imagination!

It sounds to me that the 2 "Chinese" are technical interviewers, and you happen to be weak in technical skills, or you did not fully prepare for the interview.
Also I don't think there is anything wrong with the Chinese interviewers speaking English during the interview, especially when there are other interviewers on site.
Please don't expect additional 關照 from Chinese hiring managers, I believe they care more about if the new hire can handle the work, and make their life easier.