After thinking about it, the answer is simple. When refueling, the overhead crane can pull the fuel rod assembly right out of the reactor and then set it down in the pool. No need to take the fuel rods outside. Easy transfer.
First off, it's a first gen reactor. In later models the pool is at or below grade in insanely think concrete and steel. Add to that that the pond is only meant to be a termporary storage area while the fuel cools completely down when it then can be more easily moved for disposal or recycling. Now since recycling fuel is now banned and there is no place to dump it...
Is it banned in Japan? I know that France recycles, but the US has banned it since Jimmy Carter's executive order mandated it.