hello, the amount of quadrants were thought to match the amount of routes that were in the past games. The reason that there are more than one finizen is because once a pokemon is in a quadrant it leaves the list of available pokemon. The problem is that in the sea there are so few pokemon that there are no more pokemon available so the program as a measure to not leave a quadrant without pokemon places one from the list of that quadrant.
unfortunately there will be no subsquadrant because I would have to redo all the code from 0 and the filters will not be done because I made the program in my free time and the program does not generate enough money to dedicate new options and I do not starve to death by working on it ;c