As I haven't received mine yet, this is the first good view I've had down the bowl. From an engineering view point, I can see why people report a better draw if the tube is lifted off the bottom. When all the way down, a tube would cover the holes as I see them. I saw that some one also suggested a screen to keep tube off bottom.
I don't put a screen in there. I just leave my top cap unscrewed just a bit to make a looser fit. I have an O RING in mine for easy adjustment.