I don't have the link, but apparently the Made to Order sets for the Dwarfs in Old World (Prince Ulther's Dragon Company Command & Prince Ulther's Dragon Company Warriors) have special rules that are only included in the box. Nothing about them in the Arcane Journal, if you want the rules, you gotta buy the Made to Order sets, which equals roughly £30 for four (for the command) or five (for the warriors) metal models.
So glad I don't play Dawi or have any intention of buying into them, but if my understanding isn't incorrect, this is a pretty... I don't know... and I really hope that these models do badly enough that GeeDubs doesn't think to apply such a method into other releases. And yes, I know the rules will be leaked online the day the first one arrives at a buyer's home, but I do not care for the notion of pay-walling the rules for limited release models like this.
Edit: But then I also think... wasn't this done in the past? I swear the classic/anniversary Space Marine model had unique rules?
Feel free to correct me if I have been misinformed.