Folks, there is a reason the team does not recreate tracks on a 1:1 basis because it’s a game that’s accessible to all rather than those who prefer 100% simulation and maybe want to use Forza as a tool to improve real world driving.
As much as I love hardcore realism in driving games, Forza is still very much a game and not an industry-grade simulator. The game needs to be fun to play, especially in MP, and all things considered, I’m sure there is logic behind the tracks not being 100% to scale. Also the fact that Forza uses a narrow FOV (fish eye effect) to enhance sense of speed does not help. If you put a regular cam (not a GoPro one) on the hood or bumper of your car and record a lap on any one of the actual tracks represented in the game, you’ll notice that the objects are much bigger in real life.
It may be due to these differences in scale that the track limits do not appear accurate in the game. But I’m no expert on the subject as I;ve never been to these circuits IRL. Just my two. Try to enjoy the game for what it is - it truly is the most complete racing game you could buy on the Xbox despite its flaws.