He's going to be taxed after China gets it's 50% chunk, so if China lays on a 50% tax then they would be getting 75% of his salary right off the bat.
Who are you claiming will tax him? The US or china? Of course the US will tax him, he makes his money here. As others have pointed out, the same happens to US citizens overseas. The US taxes folks and (i assume) the country they work in does as well.
If you are talking about how china is taxing him, thats a different matter, and the article itself says It is unclear whether this must be handed over before or after paying U.S. taxes.