This issue has persisted since the first Forza Motorsport on the original Xbox. The 996 911 in Forza has a painfully inaccurate model. It may have been modified for Xbox One Forza games, but it certainly was not fixed.
The entire car’s proportions are ruined. It is too tall and too short. The headlights and front bumper air ducts are too big. The front end line also goes down too quickly, causing the headlights to be placed at a wrong angle.
The rear bumper is not round and almost shapeless; really, this applies to the whole rear end. The factory wing is deformed as well. The wheels are very inaccurate, rear wheels should be more concave than the front too.
Here is the same car as it appears in the first Forza Motorsport. The wheels were unnecessarily concave back then, which was fixed for Forza Motorsport 2, but their shape is still incorrect.
I noticed that the rear end of this car in-game looks tragic because it looks FLAT!
Anyways, here’s GT7’s model of the 996 GT3. They nailed its quality and proportions since Porsche is 100% new to GT since Sport. And not to mention, the rear wing in GT7’s model is different because they have it as a 2001 model year.