Funny, I was just going to ask this.
In my opinion, it is totally random. Case in point, check out this game
(776129), between Demon Hoosiers (DII promotee last season) and King Drive Ballers (Dii Regular Season champ) from the last cup round.
No way should two highly ranked teams play each other this early in the cup.
Friends Do not Let Friends Play 2-3 Zone