There is no need to load offline maps when you are on the road. If you want to travel a larger area you may download the necessary maps upfront at a place with WiFi access - then you have the chosen maps on your device.
Probably I was too often in as situation my rental car has no or outlaste maps and no signal to use Google maps. That’s the reason why I prefer to have it locally in my device.
I will see how it works in Sardenia in a few weeks.
