Are you sure you know what you are talking about?
I don't have enough information to make a good argument, but I am pretty sure game has no idea about whether the wheel has one or two motors and does not really care, how the centering is done, it just sends the center command. Wheel does that as it is programmed to do, centers with certain force and if everything is ok, there should be no more work done by any motor once it is in center position.
Also I do not know if motors are programmed to counter each other. Iit would make sense for both motors to work synchronously in order to maximize belt traction. 2 pulleys = 2 times the friction and we don't want belt slipping, right?
I must say I haven't observed what is going on in Forza while wheel idles, because I had no problems, but I certainly will.