I mean, if you took a credit card out at 8.9% and had been using it for a few months, no-one is going to check the interest rate immediately prior to every time they use the card, they just assume it is still 8.9% until told otherwise. They wait to get a notification, which a credit company is legally obliged to send, that the rate is now say 17.9%. Obliged to send because no-one rechecks the rate before every single purchase.
It seems reasonable to do the same in the slot world. I always check the RTP before I first play a game but never scroll through help menus before every session. Would seem fair and transparent to send a quick email or a pop-up message in account to let you know that the price of play has changed…
But then I get that in such a shady industry, reasonable, fair and transparent are not things any provider really aspires to be, so its unlikely such an approach will be in place anytime soon.