Buddy, see my username? Yeah, that's a Chinese name. I of all people know exactly what the difference is between Chinese ethnicity and Chinese nationality.
With that said, the majority of Chinese business people have some connection or other to China, be it family, business, or otherwise. Combine that with the context here of mysterious purpose (but probably bioweapons), unknown funding source and complete lack of any commercial purpose, etc etc, and it's not a hard conclusion to draw.
I used the term Chinese to refer to ethnicity, not nationality.