I have seen tanks set up both ways, some with the inlet high, and some the other way around.
You are right, there is a little more draw down, but not enough to warrant changing it.
With a 315 you should have plenty of water. That is a big tank.
I am assuming this is a house well?
Most of the time if there is a cause for anodes in galvanized tanks, they will use a glass lined or it will be coated on the inside with a corrosion resistant coating.