Your health data could be used in the future, when technology is more advanced, to infer things about you that we don't even know about, and target you or your family for it.
It feels like everyone is ignoring the major part of the other side’s argument. Sure, sharing the health data can be used against you in the future, but it can be used to help you right now as well. Anyone with any sort of pain in the past will try any available method to get rid of it. And that’s fair when those methods, even with 50% success rate, are useful.
Health data could also be used now to spot trends and problems that an assembly-line health system doesn't optimize for.
I think in the US, you get out of the system what you put into it - specific queries and concerns with as much background as you can muster for your doctor. You have to own the initiative to get your reactive medical provider to help.
Using your own AI subscription to analyze your own data seems like immense ROI versus a distant theoretical risk.