When I lecture about CVI and the use of 2D images for communication, I often show these line drawings that are so often chosen as symbols for kids. The images are partial and highly symbolic. The only way I understand what the drawing means is because I have intact visual memory and cognitive abilities to make the fantastic leap in understanding what this picture is referencing. (Even with that visual memory and cognitive abilities, it takes me a while to figure out what this picture represents!)
People choose these types of 2D images for kids who are not even looking or not looking long enough to access the image at all.
Children must have any 2D symbol use built on solid understanding of the real 3D before the symbol is at all useful. We must be very careful using symbols that children can not access. It is easy to confuse lack of understanding of pictures with cognitive or language issues when they are real lack of access to the image in the first place.
Looking does not mean understanding. Holding pictures in front of kids does not mean they are looking long enough to interpret it.