guru,
I doubt it is etched in stone, but if you have close ties with an NSA official somewhere, maybe they will share with you. Having the tournament at Berliner occasionally is a very logical choice for NSA.
1) They try to host all age groups in one area, usually at several complexes. Berliner has 30+ fields. Last I heard NSA typically has something like 400-500 teams, it takes a lot of diamonds to accomodate.
2) Columbus isn't the largest city around, but you certainly need a good size city to be able to provide accomodations for all those kids and parents.
3) Ohio has had quite a number of teams play NSA in the past. That seems to be eroding a little, with PONY, and USSSA pulling some teams in other directions. I believe that Western PA also has a solid representation of teams playing many NSA tournaments (correct me if I am wrong).
I am not saying it is the best place to play this tournament, but it is a logical place to play.