I think we must wait an official answer because it's too much important and really affects game play.
My humble opinion is that the sentence cannot be separated from the paragraph, and the paragraph is all about active locations.
So the Northern Tracker helps a lot but cannot make locations disappear from the staging area: he loads them with progress tokens, and every turn you choose one of them as the active location and immediately get explored and discarded. No more than one location every turn.