The numbers don't play out because international chinese students only make up 5-7% (maybe less) of the undergraduate student body. Self-reported cheating frequencies are much higher.
That's kind of a large number. Honor system is a solidarity thing. There can be 0% cheating cause nobody wants to be that person, but if 5% come in and egregiously cheat anyway, it can poison more. Most people don't want to cheat, but they may feel disadvantaged not to.