slot rtp page showing different number on two casinos, how that work

Noticed something weird with the slot RTP numbers on two different casinos, like the same exact game but the return to player stat isn’t matching up. One says 96.5, the other has it at 94. I always figured these were just set by the provider and don’t change from site to site, but I guess that’s not how it works? Does that mean casinos can pick their own RTP from a set list or something? Or am I missing some trick with how they show the info?

Feels a bit shady if you can’t even trust that number at face value. Anyone ever bother asking live chat about it and actually get a straight answer? Not sure if I’m overthinking it or if this should be another “never again” moment.