Having a perfect spy means that the spy always has 100% chance of successfully completing a mission, no matter how difficult it truly is. However, Terhazza cannot be reached due to the combination of mountains and rivers blocking thew way. A perfect spy is still restricted by the type tiles he can move on, isn't he?
Yes, that's a perfect spy.

We are talking about the console command "toggle_perfect_spy". Press F1, and click the questionmark. Follow the directions you get then, toggle fow off and double click Terhazza