What you said still makes sense. Since there's no cellular data, Google maps wouldn't be able to draw the map therefore you wouldn't be able to get instructions if you didn't have the map saved.Ok that makes sense to me now. Appreciate the info as I’m not that technologically inclined.
So resorting to the cars navigation system made sense. I have done this in the past too and is really the only real use case for car nav these days.