Order window doesn’t really have anything to do with wait times, if you had a 6 month window and a six month wait time the wait time to get the new car is still the same!. With a 3 month window you’d still be waiting 6 months for the same car and you’d still be driving around in a Motability vehicle as they just extend the lease until you get the new car.
Please excuse spelling/typos. Apart from being a clot it turns out I had one on my cerebellum that's now causing various problems!