Your scenario is a logical fallacy. I will try explaining a different way: You get invited to those same two partys, but all you know is that one party has 4 undatables, and the other has 2. Which one do you think has the higher average attractiveness?
That is how you look at pass rate, you don't know the average score, but you do know how many 'undateables' there are at the party. KCU may have only 1, while LUCOM has 10. Which one of those parties has the higher attractiveness based on the information you actually have? And if one party consistently produces more undatable girls, why in the world would you expect it to have a higher average (as the average must include these undatable girls)?