I meant the Forzavista models not the actual in game model, and the interior model in my screens actualy use tesselation because they showed different types of autovista (Forza Motorsport 4 type, Forza Motorsport 4 type with ray tracing and the one with everything turned on with full poly car model with tesselation and shaders that where not possible at the time. you can see it on the models missing or not featured parts. But for the engine i think you are right, it is a more detailed version. I think they already have those type of models but reduce some detail so they can put it in the game without crashing the xbox lol.
And here you see the actual model used in game right now with ray tracing