That is correct. The lens is a fixed aperture and since its actual focal length is so tiny even at the relatively fast aperture of the iPhone cameras (varies by iPhone model but generally around f/2) the DOF is nearly infinite in all but very close-in shooting. As you stated, there are a number of apps that allow you to manipulate things like ISO, shutter speed, tone curves and even capture the RAW data straight off the sensor and store it as a TIF file but there is no way to change the aperture.