Even though they said that I would personally go on the assumption that one is required. Its a $650 or greater value and I doubt that FedEx will just drop it off without any signature. I wonder if you would call a few more times if you would get different answers.
In addition, Apple's website does say it requires a signature on the order summary page. You can print out a pre signed authorization slip that the carrier can collect and they would leave it at your door. Just print it out from the order summary page and tape it to your door on 9/25 if you want it to be left.