They are not refurbished because they have not never been used before. They either are off the the manufacturing line but don't come with the accessories or they are specially made with maybe one internal part that was used in another model that was defective but that particular part was working as new.
Sorry, but if I understand you correctly, that is incorrect. Service stock are indeed in most cases refurbished units. When Apple refurbishes an iPad, they replace the battery, the outer shell, and any defective components. Since Apple packages all service replacements in plain brown boxes, there is therefore no way to tell whether a replacement is a refurbished unit or new stock.