Yes, it's too dubious. Then again, i won't be surprised if they cheated because i've seen many olympics and the hosts always tried to gain an unfair advantage in order to win as many medals possible.
But we mustn't ignore the fact that all these news about cheating and all the "proof", or claiming they have the proof copied from a Chinesse source, come from the US media, without an exception. The same egocentric media that puts China second in the medals table and doctors the tables to save face and have USA as the winner of the olympics. The same country that clearly ignored countless drug offenses by its athletes in the past, Flo Jo, Jones, Gatlin, etc.
The same country that will never accept being second and will try everything to prove that they were the best.