The primary function of the app is to record a GPS activity with your phone. If you already have a GPS watch and like using it, I don’t see the point in using both. And I’m not sure about Coros, but Garmin at least give you the option to manually download your GPS traces directly from the watch without using their web services if you’re concerned about privacy.

On a technical level, federation is arguably just as compatible with libertarianism. Each instance is its own island nation, free to set its own rules while members vote with their feet in free association. That it hasn’t gone that route is more to do with the founding population than the technology.