Thats misleading. He is probably not allowed to violate the one china policy because they dont want cause problems with Chinese leadership that would hinder their efforts or cooperation. The interviewer has to know that and was perhaps trying to bait him into it. I think he did a good job actually. You have to realize here that the options was to answer the seemingly benign but actually loaded question and face (probably extreme) consequences, or to do what he did here which was to abide by chinas "one china policy".
Well, yeah, but that's surely the point? The WHO, as an international agency, is irremediably political. It has to constantly take into account political sensitivities and the fact it needs national governments, at least of the more powerful countries, to co-operate and fund it. That's why I don't entirely trust it, any more than I do the UN in general. That doesn't mean I'm going to discount _everything_ it says, but you just have to try and think for yourself about each issue, it seems to me.
I disagree with many idealist liberals I've known, who, for example, were OK with supporting the war on Iraq as long as the UN endorsed it. The UN does what the powerful countries want it to do, for example the US can bribe or bully smaller countries into rubber-stamping its decisions to invade other countries, China can demand it not contradict what it says about the virus outbreak, and so on. You can't fully trust _anyone_ in this world.
Similarly, though I'm a 'remainer', I don't have a particularly idealisitc view of the EU, compared to some anti-Brexit people I know - much of what it does is for the benefit of Germany and it's essentially a bunch of cats fighting in a sack.
Edit - I tend to assume all international organisations are at least partially corrupt, till proven otherwise. Why would they not be? See also the IOC and FIFA.