I never noticed it is missing - you are right!
Use the feedback form from the main menu bar:
Aperture > Provide Aperture Feedback
My work-around, when features are missing on the maps in the book, is to paint them onto the map in Photoshop. I print the map page of the book to pdf (Print > PDF > Save to folder as jpeg (or tiff), then edit the map in Photoshop and insert the map into a photo box.