Stravas main objective is to share information about workouts by tracking where you have been between you start and stop the workout, how could they do that wit

Stravas main objective is to share information about workouts by tracking where you have been between you start and stop the workout, how could they do that without collecting the route for the workout? The users select when to start and stop the tracking. I like privacy and think GDPR could clean up some of the mess online, but I don't even see that this tracking done by Strava is in any conflict with the law