It’s not about what you post but what data will Threads/Twitter/FB apps will trick you into sharing on system level (location etc).
They are collecting health information and a category called “sensitive information.”
Fighting to keep apps from gathering my location is old news. Many also want my photos, and I don’t trust them enough. Meta’s policy is a whole different level of creepy.
Don’t know about Android but on iOS health information is something that an app can request on OS level.
There are valid uses for this, for example hearing level measurements from third party app can be added to Health app and then used for adjusting equalizer for AirPods via accessibility options. Or your menstrual cycle (although that probably won’t make your AirPods sound better) or many other data points. This is what Threads is trying to access.
It’s similar on android. Most apps that use it legitimately relate to health or fitness. I suspect that your headphone example would apply to Pixel headphones, also.
Meta probably wants it mostly for advertising purposes. They aren’t exactly cautious when selling data, though, so who knows?
