Using Offline Maps in iOS 17: will navigation switch automatically to an offline map if online data connection becomes insufficient?

Google Maps Help states “After you download an area, use the Google Maps app just like you normally would. If your internet connection is slow or absent, your offline maps will guide you to your destination as long as the entire route is within the offline map.” I see no such advice about offline maps in iOS17. It appears you have to start navigation from an offline map, even if there is a sufficient online connection at the moment, if you believe the connection will be lost during the journey. Is that true, or will the Maps app switch to an offline map in such cases as Google claims to do?