Do we really need a 10,000 meter straight to test acceleration, top speed and braking?
Yes, we do, according to nearly every GT wish list I've ever seen. Having a real test track facility and dynamo might have been a bit better, depending on what your needs or goals are, but we are an adaptive and creative bunch, so we will figure things out.
However, if you are really asking if it justifies PD charging $2 for it, this is what we get for demanding DLC.