My dealer has lowered the AP twice since I ordered my car, both times without being asked then sent me a nice email to inform me they had done it.
My BMW dealer did the same. The AP dropped by £100 and as it was such a small sum I didn’t bother to call them, but I didn’t need to as they phoned me and said that they had done it anyway. They said to me “better in your pocket than Motability’s”. You really do find out who the good and bad dealers are in these situations. It’s less than a 5 minute job, does not affect the order at all, and doesn’t affect what they receive for ordering the car. Refusing to do it is really quite nasty and would ensure that I never used them again.