This is more or less correct, that is to say, you have now given the app the area in which the door is, but that's not exactly "where" Sense will activate.
It still uses the iOS Location Services - Significant Change feature to ready itself, then the precise location on when to "listen".
Still, calibrating location is wise to do. As Martha Stewart would say, "It's a good thing."™
As a very simplified example, you leave home, and go somewhere greater than 1km away. The Lockitron app tells the operating system "Let me know when I come back within range of 'home', which is < coordinates >."
As you come home, and get within 500m of your calibrated location. iOS tells the Lockitron app, "We're within the area of your requested location. Would you like to do anything?"
The Lockitron app responds by asking for permission, "May I temporarily run in the background and have access to Bluetooth?"
iOS complies with the request, but enforces a limit: "You have 10s to complete your operation. If needed, you can ask for more time, up to a maximum of 10 minutes."
At this point the Lockitron app starts listening for the lock. When it is within range (typically 5-15 feet depending on model and door type), it will check which version of Sense you have turned on (Notifications, Tap To Unlock, Proximity), and activate the appropriate action.