They don’t have to, and they’re not even allowed to without consent.
Thinking about how I would react if I were the astronaut in question, at first I figured I'd have no issue with people knowing about my medical conditions (in most cases). But then I got to thinking that being that open might put pressure on other astronauts to be similarly open, even if they weren't comfortable doing so.
So even though I'd be cool with being an open book, I'd probably err on the side of preserving the culture of privacy.