I've already done this. But that doesn't mean I can't call out potential privacy violations in other products.
> Also I'd rather have my data harvested for science and medicine than for selling advertisements or whatnot
Can you prove this? Even if Fitbit isn't doing this now, what if they're acquired tomorrow by a company with more relaxed morals on what is permissible to do with health data?
And all the "science and medicine" done by FitBit according to this article has resulted only in confirming things that are already known. I was actually curious what insights they discovered and there are none.
"Fitbit’s data confirms a lot of what cardiologists already know. But because the Fitbit data set is ridiculously huge, it unearthed some surprises, too."
From there the article goes on to list a number of new insights and potential research areas to pursue.
From a screenshot at https://www.cnet.com/how-to/count-steps-with-apple-watch/ the Apple Watch privacy settings let you turn step count and heart rate tracking on and off, but don't let you choose whether or not to upload them.
iCloud sync can be turned off completely on any iPhone. Anyway, I believe the health data is encrypted with some device-specific secret, but I'm not 100% sure.
Not trying to argue, just pointing out that it's not quite so simple.