When you are in freeplay in a division that allows you to freely upgrade your car such as (Forza Specials,Hoonigan, etc.) if you change car class in advanced rules it will revert to car division set to any, and vice versa. So basically if you wanted to do a race for A class Forza specials exclusively you can’t. Instead either the game will pair you with all the A class cars in the game including everthing that isn’t in your division or all the forza specials in all classes, like the new Porsche 917/30 which is in P class against you in a A or B class car etc. This wasn’t a problem before the latest update.
I noticed this last night when trying to do hot wheels forzathon.
All was good until I set a class restriction, then I had all sorts of cars. Noticed division set to any, so changed it back and my lineup was full of all sorts of different class, upon checking, now class was set to any.