I attached a jpeg of a Van De Graaff generator off the web. Is the point in the photo the Van De Graaff ground? Suppose I have a wire coming out of that slot instead of a discharging sphere, would that hole still be the Van De Graaff ground?
It is the attachment point for the ball.
Van de Graff generators don't have "grounds" anymore than batteries do.
But if you wish, you can use that point to ground the device.