Yes, the rough-in spec for a toilet refers to the distance from the finished wall surface ( not including baseboards) to the centerline of the waste flange. You can go online to any manufacturer and check the specs on their models. Typically, a toilet installed exactly at 12" would have anywhere between 1/4" and 3/4" clearance. The reason for some clearance is that the manufacturing tolerances on a large porcelain piece like a toilet are significant; and generally accepted industry tolerances on wall bow and plumb also come into play.