so the default report is "natural causes" until or IF the family decides to disclose I suppose
That's my guess. Usually if they disclose a reason (say, cancer, for instance) they often have a statement that funds donated to cancer research are appreciated, or some such. But being public figures they often don't reveal a specific cause of death, or at least not right when it happens. See Naomi Judd for a recent example - they didn't reveal it was suicide until a bit later (although some guessed that early on, they didn't publicly state it until later).
Edit - I think I read your post wrong the first time - my apologies. I read your use of the word "default" as default as in "health issues", not default as in "any cause of death". If that was your meaning, I think this is incorrect. "Natural causes" is a catch-all for health issues, not a catch-all for anything. They wouldn't list "natural causes" for someone who died of a gunshot wound, for instance, even if the fact that they died of a gunshot wound was not released. If they don't know (or strongly suspect) a reason for the death, they normally don't list the cause immediately.