To plot a route or display maps on the display only uses an extremely small amount of the map database.
And only a small fraction of that data changes during a year.
Tesla could load the entire Google maps database for the car's region (i.e., North America) once, and then when a routing is being done or the car is moving through an area, the software could check the online maps database, and download the tiny fraction of data that has changed.
If AP will be using the navigation system's routing, the data needs to be up-to-date.
And, if the map display was using cached map fragments (instead of downloading the map all of the time), the map display performance would be increased dramatically.
Tesla has designed a "best of class" car, unfortunately they haven't strived to have "best of class" software for the infotainment system.