This is absolutely correct. AT&T doesn't refurbish iPhones, they just rebox and resell. My original AT&T "Refurb" had a scratched screen and fingerprints all over it. The white box replacements may be new or refurbs, but you'll never know. 5K DOES NOT DESIGNATE A REFURB. This is where people get confused, halfway through the 3G lifecycles they stopped using 5K to designate refurbs and it now designates "Replacement" iPhone. Apple produces some replacement iPhones directly off of the brand new assembly line with a 5K serial.
This far into the lifecycle though you're most likely to receive a refurb, which is just as good as new. Unless you get lucky and the stores all out of refurbs that is.
One of the things I've always wondered is if you bought your phone from AT&T are you stuck with having to go back to AT&T?