So this is a valid point (and I admit I eat crow on my earlier statement), but not for that reason. In that photo, there are three fingers in front of the cup, but you would not expect 5 fingers because the way humans hold cups, the thumb will be occluded by the cup itself. That said, I don't think there is a way to hold a cup with both thumb and index occluded, so the correct number of fingers would be 4 in that case.

If you zoom in, the index finger is just obscured by the middle finger. You can also see the knuckle, so it's not incorrect, just an awkward way to hold a cup.