Truth. Originally you could not edit picks at all after you made them. This was changed when lots of top seeds would withdraw and people would end up with REALLY small totals for events. I made it that you can only change when seeds withdraw because if it were when anyone withdrew, there would be so many changes all the time.
It is INCREDIBLY time consuming to run this game (it would take about 6-7 hours a week depending on the size of the tournament, plus doing the total rankings), and it makes it more difficult everytime someone changes a pick. When I was running this game, I would pray every week that no seeds would withdraw so I wouldn't have to deal with going back in and changing everyone's picks who replaced.