Stranger than fiction. And yes, P. hangianum is listed in that book as from China. Yunnan, if I recall correctly.
Just to clarify, P. delenatii has still only be found in southern Vietnam?
Delenatii has been found only in central-south Vietnam, around Dalat to Nha Trang.
It's normal about hangianum being listed from China, they have so many plants and hybrids, and it will be a way to legalize their plants. Hangianum never comes close to the Chinese border in fact...