There are some statistics that is surely available for public somehow related to that, but I currently don't know where to find it... haven't tried using search engines yet.
There is currently a trend here on our country with different fiat casino popping up, I am sure that those were able to churn some of their players' pockets.
It depends to the casino, better play to those that had already gained good reputation than trying new & suspicious one.
Generally, I don't get the difference how can fiat users be churned like that compared to crypto players. I mean, those are just same players with generally almost have the same gambling knowledge.