well, certainly it's possible to fool yourselves with A/B testing, it doesn't mean you must be fooling yourselves. I've also seen similar results in recommendation settings in mobile gaming, not once but over and over again across portfolio of dozens of games/hundreds millions of players. You don't need to predict 20% better on whatever you are predicting to get a 20% increase in LTV and it's even better if you are doing RL since you are optimizing directly for your KPIs