Yes, the drawing seems a bit squirrelly. You can place walls atop each other, but as I mentioned above, they have to be on different workplanes or Z heights; normally whatever the actual height of the wall would be. Once the wall or its components (door, window) goes above its height and into the other wall, you get interference problems (X's in walls, etc).
Designer, Deluxe, (Professional, Expert, Basic), Platinum
Windows 10 Pro (1803), 64-bit