People are getting upset about this but it's been standard behavior in the app for several years to make waypoints on public routes public by default.
The change was to make waypoints on private routes to be public by default, which AllTrails has indicated in the thread they will be reverting and adding a new option to mark waypoints as public or private by default at the account level.
Not cool at all, that's where I keep my favorite fishing spots I've had to bushwhack to find. Everyone please overt your eyes while I go on a screenshot and delete spree.