It looks like R3E uses a generic rectangle ambient shadow for all the cars. If you look at the FR2 you can see the shadow doesn't match the cars shape exactly. Using it in the same way with the FJs would result in the shadow extending out from under the car body. From my limited experience with modding Race07 (fixing bad conversions for personal use) this contact shadow was a unique image per car which is probably the case with other sims. This way the shadow image can have the contact shadows for the 4 wheels and ambient shadow for the body all in one image. It is most likely a rectangle in R3E for performance reasons, now more than ever with multiclass races.
Shame, it's not a deal breaker, I'll still keep driving these fun cars, but hope something can be done about this in the future. Though please release ADAC 2015 first!
Think it's a mixture of what Dan said and the fact that I believe initially there were no plans for open wheelers in Raceroom. It's not that noticeable on closed body cars and it does reduce the load I guess, so back then this was good enough. That's why I said "for the time being" above tho. Idk if there are plans to fix this in the future. All I know is that the devs are aware of the issue and looking into possible improvements.
It's the same on all cars. Just most obvious on these as the wheels are that open and far away from the bodywork. Kinda funny that nobody noticed before and now it's like the worst thing ever... ^^ No arguing tho, it doesn't look right and if possible it will be fixed for sure.
I guess, as the bodywork of the GR2 is a bit wider, the missing shadow is not so noticeable on that car. On FRJ there is nothing around the wheels which made it pretty obvious...