It is not hidden, but maybe they did not announced publicly. As we all can see here https://help.stake.com/en/articles/4821738-what-is-rakeback-how-it-works-and-how-to-get-it and as confirmed by live support, the rakeback is now 5% only. The same information is also available under the VIP club page, but the information about when it is changed is available in the help center page. The article about rakeback is updated this week. Anyway, I dont understand why Stake cut it 50% off, but I think it may affect some players and may leave Stake because of this change.