Our walls are already wallpaper-ready

Our walls are already wallpaper-ready. These don't need to be sanded, right? Often they do. If you were to apply Renovlies directly over a wallpaper-ready wall, you would see all the imperfections. Why not have it done properly straight away? You will probably be looking at your walls for a very long time. If we were to paste over your walls without any pre-treatment, everything underneath would be visible. Every bump, every hole would be highlighted. The minimum is sanding and filling. If a wall is built from sand-lime brick blocks, which are often unevenly stacked, plastering is a requirement.