WHO does rely in large part on donations. See http://apps.who.int/gb/ebwha/pdf_files/WHA72/A72_35-en.pdf page 82. It could certainly be argued that they have an interest in convincing China to boost the voluntary portion of its contribution to match that of some of the other nations on that list.
WHO has "assessed contribution", which is its lifeline upon which it relies. I'm not saying it doesn't accept donation. just that WHO doesn't need donations to survive. It's clearly shown in the pdf which you linked here that China doesn't even make it to the top 10 donor list. Donation from the United States comprised of 76% of WHO total voluntary contribution. Why would WHO risk angering its major donors and pleasing to one specific small donor? Even if finance were taken into consideration, it still doesn't make any sense.
