Originally Posted by
soviras
You seem to be missing something. Each girl is a drop of it's own with it's own roll. It doesn't roll 1 time to determine if you get a girl and then choose the girl, it rolls one time for each girl you can still get and then if you had a successful roll it will give you the girl you had a successful roll on. If you didn't get any girls from Grunt (as an example), then there are currently 4 rolls for girls, one of which is the higher chance event girl. You can get any of them at any time, but only if the roll for a specific girl is successful.
If they made the girl drop always be the event girl if one is available, it would create more issues than it would solve. For instance, the event girl drop chance would be much higher for someone with no girl drops compared to someone who had all 3 normal ones already if every successful roll gave the event girl. If we simplify the situation and make the odds for the event girls and normal girls equal at 1/1000 and use simplified calculations, then this should explain the issue with it:
1/1000 * 4 = 4/1000 = 1/250 chance to get the event girl with 0 girls obtained from grunt/dark lord, 3/1000 = 1/~333 chance with 1 girl obtained, 1/500 with 2 girls obtained, 1/1000 with 3 girls obtained.
The odds are only an example though (we don't know the real odds), and it's not fully accurate, but it's close enough.