I think you refer to the preset RTP values, which scale, and the casino may choose the concrete RTP value when procuring the game from the game provider. This is quite a common practice and the reason why we always say the player should be able to see the current RTP value available to him for each game.
Please do not mistake this for the most widely held player belief, which is that the casino somehow changed RTP specifically to lower players' chances of winning. As long as each game has an RTP below 100% and players continue to play in hopes of winning, this is totally beyond the realm of rational discussion. The mathematical advantage is always on the casino side, so they actually just need you to stay; you will lose eventually. Furthermore, despite being the least favorable of all casino games, the majority of players continue to play slots.
Under such circumstances, casinos only need players to participate, and players are more than willing to play the most disadvantageous type of games—the slots.
Have you ever thought about this before?
Of course, from time to time some scammy casinos simply chose the shortcut to profit and used some sort of fake games.
Actually, though, I would not waste time on phony games if I wanted to start defrauding players; instead, I would entice them with incredible bonuses and an unclear deposit requirement to authorize pending withdrawals. Once I had enough, I would simply close the site. Based on my personal experiences, I believe that this is an easier and, of course, the most unethical method of scamming casino players for money. No need to bother with "altered RTP"...
Automatic translation: