The question was if RTP of slot games can be adapted to casino preferences. Well, let's say not adapted but the FACT is that casinos CAN choose RTP settings if they are available on software provider's side.
Look for example, the latest release from the Nolimit City game provider:
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There are two RTP settings options: 96.09% & 94.13%
Some providers have more RTP settings options, like Pragmatic Play (3 RTP settings). And some, don't have options of lower RTP settings, just default/top one.
I've been meaning to research about this but didn't know where to start, so where did you got this data from? And is there any way to know what settings different casinos are using? I want to make a spreadsheet for my own amusement comparing slots rtp in different casinos.