Coordination is about controlling all of your body parts while doing different activities. It is about making and maintaining
connections between the brain and the muscles that control movement. For a child in a wheelchair there's an additional step of translating this into moving the wheelchair which adds another level of complexity.
Hand eye coordination takes on a different meaning when pushing a wheelchair. When pushing a wheelchair, the eyes need to be looking up and in the direction of travel, not on the hands themselves. It's like driving a car - you wouldn't want to watch your feet to accelerate and stop. Proper stroke mechanics learned early will help to "automate" this process and allow the child to focus on more complex coordination challenges like catching a ball.