I have a few thoughts on this,
A VIP employee once wrote to me, that all people's wagering (or deposits) is randomly being distributed with a RTP of approx 97%. So games are always within bound to the limit on what people wager on average. This is called server sided gaming and it makes sense. Local casino's do this for a longer time. Big blocks of 12, 16 machines, all people's wagering equally distributed or some shit. You cant really break the casino by this model, and that's exactly why they are deploying it. This goes out for the slots tho.
Some games are at the beginning very hot, being played alot, and at some point new games come into play. To make the new games now more hot, the RTP is being set a tad more positive to the new games, and the older games gets less. This seem to be in effect from games from one and the same provider. I can get a really good shot at one game, and have a terrible result on another game. I used to play one particular game by Pragmatic, this fun pretty much ended not so long ago which kind of made me force to play another game.
Trust me, i came back with a bankroll big enough to last as long as possible, to be finally beat down and have the worst day of my life feeling. You know they changed something when you cant hit spacebar anymore which make the spin instant stop. You have to kind of sit it out. A important element is taken out of the game, and thats when you know, they've touched it and mangled it down.
The game with the cups, i dont know the name, but i've punched nummerous (buying) sessions and finally getting wrecked over. Out of 50 buys only one retrigger with a lowzy, 5 extra spins came along. Bonus buys in between 100 and 2000 euro. That game was nerfed as f. So yeah if a casino states we offer 97% RTP, and as long as it counts in the numbers its legal, right? The way they implement that is up to them. To me it sounds very unfair if these where practices that are slowly evolving, just to keep a longer hold-up time, just to extend players playing some more, and more important, depositting more. The variance online is just crazy.
Landbased i could tell hey this will hit in less then 5 minutes. Online? Geezus.