Also if that formula you provided about chance to win depending on Stamina is correct then whales would not need event girl with 100M stats. The minimum chance to win with 4k stamina would be 5% and then they can just retry event battle with base untrained girl for 20 times on average for each win. Resetting the timer for battle costs 1 gem(?, I am not sure about this, I have 14 minutes left and it shows 1 gem cost, don't know how much it would be for 20 minute reset), so finishing event even with untrained girl and Santa's final stats at 100M range would cost only 300 gems on average if you follow this tactics. So even based on proof you provided we can't see that theory that is being discussed is wrong.