If you order a product and it is going to take an extremely long time to receive it. I don't see nothing wrong with calling. You would just be asking to recieve the product just as the other people who ordered just some hours or a day before you that isn't asking much, special treatment no.
From past multiple years of doing this, Apple wants to ship as many iPhones as quickly as possible to as many people as possible. While asking doesn't hurt, it actually doesn't help either. It more of feeling like you have a bit of control, when in reality you don't. Quoting a week earlier delivery time is simply taking out any float that was in the quote to begin with and would have be done automatically if at all possible.
Anyone that got an improvement, may now be disappointed if their is the slightest bit of hiccup and the date slips. By design Apple provided the for sure date first, always intending to improve on it if at all possible. Apple does not have any reason to delay shipping product that is available.
Interestingly, what other phone receives this much attention upon release. The excitement and anticipation is something other manufacturers would love to have. In effect marketing by the consumers. Free every year.
