What you think that they can or cannot disclose is what is truly irrelevant, you are basing your entire argument on the assumption that you know what they are and what they are not forbidden to say. You can't make that claim, only presumed generalities that may or may not apply. You have no idea how much leeway Zarhym was allowed in his time in the job.
All we know is that Zarhym made a statement saying there were no plans for Demon Hunters and that there probably were. Either he was lying or he was ignorant, and the likelihood is he was ignorant. That is it and nothing else.
Your argument doesn't make sense. You are trying to force an equivalence between the game director and a community manager, ignoring seniority and the fact that the game director is going to be privy to a lot more secrets than the community manager. What the game director says carries infinitely more weight than the Community Manager.
I mean seriously, pro High Elfers attack what Ion said on the grounds that he doesn't know what he is talking about, he's an idiot, he hates the Alliance etc. and here we have an argument that we should put more faith in one of the old PR guys because he said something on a completely unrelated topic!
And they didn't say 'not now'. They listed the reasons as to why it shouldn't happen. Namely that they undermine the faction wall, and they are already available in game. Those are factors that are not going to change no matter which expansion we are in. He gave a firm a no and just tossed out a standard platitude at the end that maybe someday they'll reconsider.
Given the reasons he cited in opposition though, it's going to be a doozy of an ask.