Mainly that they sell health data (anonymized and aggregated, but still), to undisclosed third parties and they're not super upfront about it.

I can’t find this information and there are way too many policies to sift through. It doesn’t seem unlikely or abnormal, though. Do you think many wearable manufacturers aren’t sharing or selling data like this?

This right here. When I see a twenty buck wearable I immediately think surveillance.