I think if you look closely, it has a pickup tube that runs inside from the winterizing fitting on top to the bottom of the tank.
I have a short hose running from the top of the tank to the 2 way valve on top, a long hose that is the input for winterization, and then the output from the valve to the pump.
The drain line runs from the lower rear end of the tank to the drain valve at the rear valve compartment.
There is a fill line and vent line running to the forward right side of the tank near the top.
No openings on the bottom. This is an '05 model.