Creep is a result of the amount the inner pages are pushed out away from the spine during the binding process. The effect is that the outer pages will be trimmed to the books specified size, and therefore the work can be positioned normally. As you go further into the book toward the center spread the trim sizes of the pages from spine to face will get progressively smaller. This has to be adjusted for by shingling the work on those pages in away from the face trim by an appropriate amount. In preps, the software is able to adjust for this by moving the work in from the face and toward the spine on pages as they progress to the center of the book. The outermost 4 pages would have no adjustment made, but the bulk of the outermost pages has to be accounted for when applying shingling to the inner pages to adjust for their creep.
So, in answer to the question, yes preps must know that the book has a cover so that inner pages are adjusted, but as the outermost form it will not be shingled since there is no creep involved. Creep has to be adjusted for based on total pages in the book, not by the number of pages in any given form.