As far as I know, Carnival hasn't clamped down on their player bank system on the slots. You simply put your cruise card in the slot machine, follow the instructions to create a player bank, deposit whatever amount you want from your shipboard account to your player bank, and play or cash out whenever you want. There is a daily limit of something like $2000, but it's fee free and is simply charged to your ship account, which is then charged to your credit card.
It's been this way for at least 6 years, across all the Carnival family of cruise lines (Princess, Holland America, P&O, Costa etc). One would think this is easily abused and therefore Carnival would cut down on it, but I think they make so much off of people who gamble more this way that they find it worth it for people who use the system as a mile-earning ATM.