I believe that the first four permanent circuits of the Gran Turismo franchise (Trial Mountain, Deep Forest, Grand Valley and Autumn Ring) were idealized without any reference to reality. Racetracks were created according to the PS1 hardware limitation, according to the aesthetic sense of the PD designer and the trends of racing games at the time, such as Daytona USA and its tunnel scenarios, huge rocks, constant elevation change etc.
But, from the beginning, I believe that the famous SSR 5 and 11 were inspired by Tokyo Expressway, considering the side walls that look like hollow brick bathroom wall.
So, as technology advanced, Kaz and the PD guys effectively got into the habit of creating circuits with some reference to reality. They started doing this with city circuits (Tokyo, Amalfi Coast, Paris, London etc.) and some in the mountains like Grindewald, El Capitan, Eiger Nordwand etc.
The era of GT7 arrived with the requirement to nail the circuits somewhere on the world map and its panoramic views of the race waiting screens.. I think Kaz and team felt impelled by tradition to remake the original four permanent circuits and locate them in some region of the real world. So they researched and researched, and, good or bad, came to these current conclusions. I believe the same will happen with Apricot Hill and Mid-field Raceway.