I think the two major contexts here are luck and preference. Basically some gamblers prefer some casino games over others mostly because of their win rate on that particular game and they will usually pick the car similar that is most flexible for them to reach those winnings and it's a normal thing.
I think I will disagree with you in terms of preferences because the incidence that OP is talking about here is something that I can relate to more, basically you can prefer a particular casino or sportbookie but win more in another casino or sport bookies. this is exactly what OP meant, so I believe that it's just a coincidence that people get lucky in some casino high than they are in other casino.
I have also seen someone complain that he has never won in a local sport bookie that everyone enjoys in our locality (sportybet) meanwhile whenever he happens to use another like BetKings he wins more. That's just mere coincidence in my opinion.