I know Prosthetic, but it is really not so common to seek for a full logic on community boards
I am perfectly aware of this issue, I have reported it myself few days ago and many of us who have the 900 wheels and playing this game for *serious* are 100% aware how some kind of assist - I prefer to call it
buffer, since I find it doing the same as infamous "steering buffer" from Forza 3 - is in place. At least at this demo.
I am still waiting for the full game in order to see what is going on. Since this demo does not provide us with nay adjustable option regarding wheel, it *could* imply how some issues we're experiencing comes because game itself can't really know what wheel are we using.
Lack of HID controller in Xbox console means that hardware have to rely on wireless connection in order to detect the device. And at this point we have one generation of 270 wheels (Microsoft, Logitech), Fanatec 900 wheels and new Microsoft Speed giro-controller (I will never call that device a
wheel 
) for a game to recognize and adjust the steering.
Maybe, just
maybe there is some hope we will get rid of that horrible buffer.
My hopes lies in fact how Demo can't really recognize 900 input device until you actually perform a "S_1/S_2" trick and it could lead in full recognition when options become available.
If not, than it is clear how buffer is still there. And no word from no person - even main developer director - can't assure me how the fact I can't force F458 to spin unless I really kill it with oversteering is because all assists are off and car should behave that way.