You are right about that. I think the last few numbers in the VIN are sequential for how they are built. However, delivery can vary. Some trucks are shipped to outfitters to have other parts installed. Mine will go out for the spray in Bedliner.Very Very Low 600K range.
But I'm not sure this has anything to do with who will get theirs first.
Wanted to bump this back to top and see if any posters here in low 600XXX vin numbers had received their truck or know their expected delivery dates. Other posts indicate they are arriving now!