“Well, the twitter user who posted this lives in Hong Kong, I assume he/she would have noticed the discrepancy. But maybe not.”
Especially of late, a lot of Hong Kongers are not exactly fond of their brethren in the mainland, so he/she may have wanted to intentionally foster some more bad feelings between the US and China?
I have to say that these reports of Chinese purchase of masks gives more credence to the releasing of the CoV virus across the world on purpose. Send out people to buy up masks from other countries and then send the virus around the world. Great way to bring the world to it’s knees. China has a lot more expendable population then most every other country.